NEW YORK WHOLESALE

But, the truth is that cross-Channel shopping can still be financially worthwhile. For my trip, I devised a list of 13 well-known brands (Gordon's, Jacob's Creek Chardonnay, Moët & Chandon brut and Martini Bianco among them). If I had bought them all online in Britain from Sainsbury's, they would have cost £194.12.

At Sainsbury's Calais branch, the same brands, in the same quantities, cost £163.06. That's a saving of £30, or about 16 per cent. Trawling round Calais looking for the cheapest-possible version of each brand reduced the total further, to £146.94, saving 24 per cent.

And, of course, my test underestimates the possible savings. By picking well-known brands, it ignores 99 per cent of what's available, often at more substantial savings. Offers of 50 per cent and 60 per cent off British prices weren't rare. The test also ignored special deals ("Buy six and get one free", etc), which are widespread – and the fact that some shops operate a better than £1:€1.11 exchange rate. Majestic's Wine & Beer World and Oddbins offer a rate of £1:€1.30, as long as you pay in sterling with cash or by cheque, and Sainsbury's is currently offering £1:€1.33 for sterling cash.

So yes, a trip can be justified, especially if you live in the South-East. And, at almost all shops, you may order by internet before you travel, for collection on arrival.

To make it financially worthwhile you must:

(a) buy at least £250-£300 worth of goods

(b) concentrate on wines and spirits, where the savings are greater

(c) get the best cross-Channel deals – or use those Calais outlets, such as Oddbins and Majestic, that will fund your ferry crossing if you order enough (see below).

Before you do anything, check that the exchange rate hasn't got much worse.

Where to shop

There are three key buying zones, all on the fringes of Calais. Please note that prices of individual wines may vary according to promotions and exchange rates available in each shop.

Marcel Doret commercial estate

Come off the A26 motorway at Junction 3 – the first after the ferry – and follow signs for "ZA Marcel Doret". You won't miss EastEnders (0033 321 345333, www.eastenders-calais.com) It announces itself like an ageing fairground.

It's probably best known for its bottom-end own-brand wines, which, despite some tasteless labelling, are of reasonable quality. The place has cut back on beer, but still stocks high-standard wines from across the globe, and then some classier ones that you are surprised to find in a vast, cold shed.

A Château Beauséjour 2002, from Montagne St Emilion, at £11 and Lynch-Bages 2000 at £78 catch the eye. EastEnders is open 24/7, and it's tight on prices. Of our 13 brands, it was cheapest on three, and competitive on most.

Almost next door, Wine & Beer World (0033 321 976300, www.majesticinfrance.co.uk) is the Calais arm of the British merchant Majestic. Though still big and cold, it's more what you expect from a retail experience – there's paint on the walls.

Beers, spirits and world wines are well represented and it also passes my test for a plonk shop: that there be an interesting range from southern France. With a Château Flaugergues 2006 at £5.98 and a Château Pennautier Cabardès at £4.50 (£3.49 if you buy six), I couldn't complain.

Order for £300 on the website or on 01923 298297, and use the reference number given to you to book a SeaFrance day return, and the shop will reimburse you for your Channel crossing (terms and conditions are on the website).

Just off the nearby roundabout, there's no doubting the serious Frenchness of La Grande Boutique Du Vin (00330321 972122, www.vinscph.com) The salesmen wear sommelier's aprons, there's a temperature-controlled cave for fine wines and one of Calais's two best ranges of French produce.

A belting champers selection (the company is based in Champagne) runs from Louis Chesnel at £11.46 to Bollinger Special Cuvée at £25.25 and beyond. And the place easily passes the southern French test with, among many others, a Provençal Château Réal Martin white at £6.38 and Domaine d'Aupilhac for £9.54.

Cité Europe

Off the A16 at exit 41 or 43, and hard by the tunnel terminal, the keystone of this mega-shopping centre is the Carrefour hypermarket (0033 321 467646, www.carrefour-calais.com), which offers the advantage of booze, food and toy shopping in one place. The food shelves are especially well-stacked, and the wine section is strong on cheap and mid-range French stuff at good prices.

Good on spirits, too – and just along the mall is Tesco Vin Plus (0033 321 460270, www.tesco-france.com) Those familiar with their British outlets won't be disappointed, especially not at the frequent "50 per cent off UK Prices!" notices.

La Française commercial estate

Along the road from the Cité Europe, same motorway exits, follow signs for Auchan (0033 321 978339, www.auchancalais.com), a consumers' temple quite as abundant as Carrefour above. Across the car park, the main range at Sainsbury's (0033 321 823848, www.sainsburyscalais.co.uk) is as you would expect – sharply priced own brands, spirits and New World and European plonk.

Alongside, though, they have wheeled in some of Bordeaux's better wines, complete with a sommelier. If you look serious enough, he will let you taste a 2005 Château Pape Clément grand cru Graves, which sells for £115 a bottle.

They are also focusing on half a dozen smaller-scale French producers from unfashionable spots such the Corbières and Côteaux-du-Layon.

Nearby, Oddbins (0033 321 190019, www.oddbins-calais.com), an independently owned outpost of the British business, has a well-priced standard range (cheapest on two of our 13 brands) but its real strength is in good and diverting wines from pretty much everywhere. Including the South of France. I'll go for the Copa Santo from Domaine Clavel, at £12.99.

Oddbins also has a lot more wines under £2. You may taste them at the counter and, believe me, the Altana di Vico Italian red at £1.49 (£3.50 off British prices) was a lot better than the house poison in a Calais brasserie that night. If you order goods worth more than £200, Oddbins says, it will provide a booking reference that entitles you to a free day return with P&O.

And finally...

Away from these three centres, by exit 44 off the A16, Calais Vins (0033 321 364040, www.calais-vins.com) is overseen by Jérôme Bont, who entices you to his tasting counter – the best in town – at the slightest glimmer of interest.

The basics are well and economically handled but real enthusiasm is reserved for a spectacular range of spirits, and the second of the two finest French wine selections in Calais. If you're interested in wine, you'll be browsing through to closing time. "My pleasure is not to have a big car," said Pont. "It is having a vertical of Lafite in my cellar."

Eating out

If you have time to enjoy a meal after your shopping, you will dine well near the town seafront at the Sole Meunière (1 blvd de la Résistance, 0033 321 344301, www.solemeunière.com; menus from £15) or next door at Le Channel (0033 321 344230, www.restaurant-lechannel.com; menus from £16.50). At the other end of town, Au Calice (55 blvd Jacquard, 0033 321 345178, www.opalenews.com/lecalice, menus from £14) is a bustling, good-hearted brasserie and open late.

Getting there

Seafrance (0871 2222500, www.seafrance.com) sails Dover-Calais 15 times a day, with online day-return fares from £25 – for car and up to five passengers.

P&O (08716 646464, www.poferries.com) day returns start at £29, for car and up to nine passengers. Eurotunnel (08705 353535, www.eurotunnel.com) services are currently restricted to one every 90 minutes (two at weekends) because of the fire damage to the tunnel. Day and overnight returns start at £44, but you will need to book early, and off-peak, to get these prices.

Norfolkline (0844 847 5042, www.norfolkline.com) offers a Dover Dunkirk service.

He sold his plant centre in his thirties, went travelling for a year and returned to take up a job with Crocus at its inception, originally as the products buyer and then switching to plants buyer. When Tom Stuart-Smith asked if Crocus could supply a full plant list for a job, Mark found himself looking at a spreadsheet that was 1,000 lines long (the garden was Broughton Grange in Oxfordshire). “To source all the plants on a list like this is hugely time consuming, very stressful and you’ll get let down with every excuse you can think of,” says Mark in his famously direct way.

“But the good thing is that once you start doing it on a reasonable scale, nursery people start taking notice of you.” Requests for supplying Chelsea gardens followed. “Our ethos, which I quickly learnt by doing Chelsea shows, is that there’s no such thing as 'no can do’, so when I heard, 'Oh, I can’t, mate,’ or, 'Oh no, mate, it’s five minutes past five,’ I immediately got rid of them and surrounded myself with people who can do.”

He admits to doing a fair bit of shouting and swearing when suppliers don’t deliver – a trait that Jinny Blom, who’s a close friend, recognises but says, in his defence, “He only uses his appalling temper to get a better result.” With his reputation for seeking out only the very best specimens, he soon built up a little black book of top-notch nurseries such as Orchard Dene, Phoenix Perennials, Howard Nurseries, Woottens, Fromefield and Chichester Trees and Shrubs from the UK; Jan Spruyt, Laurica and Solitair from Belgium; Lorenz von Ehren from Germany; and Lepage from France.

Finding the plants and keeping an eagle eye on their progress – with the plants that need to overwinter in southern Europe, this means frequent trips to the nurseries – is half the job. The other half, he says, is “managing expectations” – shorthand, I detect, for managing the designers themselves.

Some, such as Stuart-Smith and Jinny Blom, have a very clear idea of exactly which species they want; others (naming no names) will say, “I need big, white, towery stuff for a shady spot.” Even with experienced designers, he has to scrutinise their lists carefully. “When I discovered that Ulf was expecting his Salvia nemorosa 'Caradonna’ to be three feet high – the height they reach at his home close to the Arctic Circle – I immediately let him know that we could not get them to that size here.” Designers add to his stress by not coming to the nursery to see their plants or at least phoning to check on progress. And then in the run-up to Chelsea, he says, they all panic. “They get to see drawings of all the others and they all think 'mine’s rubbish’. And in the week before the show opens, it’s the Tuesday that’s particularly manic as the plants that the designers have usually sent back the day before have to be loaded on to the lorries again, because they’ve changed their minds.” Mark doesn’t get annoyed with these last-minute substitutions – it’s part of the job – but it is a logistical nightmare. And of course every year there are plants that have either gone over or haven’t come far enough on, and the ones that crash off the trolleys or are demolished by reversing lorries. That’s partly why Mark grows four times as many plants as will actually be used.

Why does he do Chelsea, apart from the obvious financial gain? “I have no idea why. It’s certainly fun at the beginning, sourcing the plants, but by the time showtime arrives I can’t stand the idea of going up there.” But then he admits, “It’s really important for me that the gardens get a gold. Your whole heart and soul’s gone into it and you become friends with the designers because you’ve been through hell and back with them.” This year he’s excited by the burnt orange Verbascum 'Petra’ with a velvet shimmer grown for Joe Swift. Two grasses have also caught his eye: Molinia caerulea 'Dark Defender’, a mid-green grass with elegant leaves and black flower stems that stay on for a full year, raised by Marina Christopher and being grown for Andy Sturgeon’s garden; and Deschampsia flexuosa, an “absolutely stunning dark green grass” chosen by Sarah Price for

The Telegraph Garden.

It’s Sarah he picks out as standing a very good chance of winning Best in Show. “She’s moved away from the obvious Chelsea garden shapes and structure and is using lots of lovely water plants. It’s all coming together beautifully,” he says.

The same could be said for Hortus Loci, which is destined to become a one-stop shop for top landscape architects and designers.

Hortus Loci, Hound Green, Hook, Hants (01189 326 495; hortusloci.co.uk)

On Rua do Loreto, I step inside the wood-panelled Casa das Velas do Loreto (in the same family since 1789) and find tall, honey-scented ecclesiastical candles for £15. At A Vida Portuguesa, on Rua Anchieta, my heart quickens at the fine Portuguese soaps and beautifully-packaged tinned sardines. Junk stalls in the Estrela park yield some irresistibly touching, framed black-and-white family photographs from the 1930s, costing a few euros each. Exploring the new waterfront design area, Santos, provides a satisfying few hours.

Back on Rossio, at the the 120-year-old Chapelaria Azevedo Rua, I finger a handmade man's fedora for £57 – the double of one I swear I saw on Jermyn Street at £120. I postpone checking out handmade riding boots at Vitorino de Sousa on Rua dos Correeiros. And it is just as well that, before I hit the antique shops of Rua de São Bento, I meet the art-restorer owner of the new Palacete Chafariz del Rei boutique hotel, a 1906 mansion he renovated. "Lisbon has great antique stores," he says, "but so does Oporto – and 50 per cent cheaper." So it's advisable to take a large suitcase there? "A van!" he says with a grin, and points to a beautiful 1920s leather sofa and chair bought for £170.

How to do it

When to go
Any time, but May is best: it's not too hot, the purple jacaranda is in blossom, and you can take a 30-minute train ride to the beaches at Cascais – home now to the Casa das Histórias, showing the surrealist work of Portugal's brilliant Paula Rego. Bear in mind that Sunday is quiet; only museums open.

Where to stay
On the outskirts, the Lapa Palace and Pestana Palace hotels are very grand, but all the chic new spots are central: LX Boutique, Inspira Santa Marta and, just off Rossio, the Altis Avenida (00 351 29 172 4307, portugal-live.net; rooms from £115), with young staff, black-carpeted rooms, a spa, and a seventh-floor roof terrace brasserie. For more information, see visitlisboa.com and flytap.com

What to do
Pack flat shoes: you will walk a lot. On arrival, get the Convida Lisboa shopping guides, free at all hotels, and a three-day Lisboa Card (£28) for the trams, Metro and buses. In bustling Baixa, see the new Mude design museum (mude.pt); in Chiado, old shops; in Principe Real, new design stores, cool cafés such as Orpheu, and boutiques such as Kolovrat (lidijakolovrat.org) at Rua Dom Pedro V 79, for witty printed silk scarves and spider-web silver necklaces costing £330. Go to Bairro Alto at night, for the bars, and medieval Alfama for almost hilariously mournful fado. Hottest area: waterfront, ex-industrial Santos, buzzing with lifestyle stores, bars and restaurants; see LX Factory (lxfactory.com) and Ler (lerdevagar.com).

Where to eat and drink
Have cocktails at new, glass-walled Le Chat (00 351 91 779 7155) at Jardim 9 de Abril. Have dinner at rough-chic 560 (00 351 21 346 8317, restaurante560.com) at Rua das Gáveas 78: wild mushrooms in Azores cheese, swordfish with banana, then pineapple carpaccio with coriander sauce. Finish at the new Sol e Pesca bar (00 351 21 346 7203) at Rua Nova do Carvalho 44.