Cheap Chic: How the High Street got its groove back

Stella McCartney has taken it by storm. Betty Jackson and Jasper Conran also design for it. Kate Moss shops there

She'd like to be Peaches Geldof, but has to settle for an ordinary name. She'd be very happy to cut off all her hair à la Keira Knightley, if it meant she got to smooch Orlando Bloom. And, crucially, she really, really wants Sienna Miller's wardrobe.

That is where today's teenager is in luck. For the high street, where she has shopped from necessity, is now where Sienna Miller will have to shop if she wants to maintain her iconic status. Heavy hitters from the fashion industry are brokering deals with chain stores; the results are getting fashion people excited and are like a sprinkling of fairy dust over the fortunes of H&M, Marks and Spencer, New Look, Topshop and Miss Selfridge. Debenhams has hired some of the most fashionable British designers to produce collections. John Rocha and Jasper Conran provided a glamour that helped the chain sell £2bn worth of clothes and goods last year, a new record. Betty Jackson has joined the effort with a new collection called Black.

Then there is Stella McCartney, who has taken the high street by storm in the past few days. There were extraordinary scenes on Thursday when the McCartney for H&M range went on sale in 400 stores in Europe and North America. Branches were quickly stripped of silky vests, tuxedo pants and that double-breasted trenchcoat. Teenagers came out in force: H&M is the mother lode of cheap, cheerful and trendy clothes for nights out. But joining them, elbows out and babies cast aside, were women in their thirties with highlights and heels. Worlds had collided in search of couture cool. The buzz was palpable, and the queue for the checkout snaked around the shop floor. At 8pm, a weary assistant explained, the fourth delivery of the day had just arrived. An ambulance idled outside, waiting for a potential changing-room casualty.

Fashion is, as someone once quipped, "so ugly they have to change it twice a year". So this turn of events, in which the more "directional" items get copied almost as soon as the supermodel turns off the runway - to appear in high-street stores what seems like nanoseconds later - means more power to the customer. Who wants to spend £1,000 on a floaty Russian-inspired dress in Burberry when Zara is turning them out for less than £40? The same goes for the skinny jeans that are so in demand up and down the country. That's £140 for the Superfine ones Kate Moss is so fond of; Topshop have a perfectly cut pair for £40.

Grown-up women, meanwhile, think beyond wanting to wear today what they saw Sienna photographed in yesterday. It's the "disposability vs investment, cheap vs quality" argument. While the teens will wear their McCartney vest with chain detail to a few parties, then discard it, women in their thirties will wear the trenchcoat or the tuxedo pants together with something rather more expensive - and get ready to respond to inquires with a smug "it's from H&M actually". And that is the true appeal of this trend; the reason why those grown-up women will face the indignity of joining the queue outside a Zara changing room, or the near-riot levels every Saturday morning at their local Primark.

Marcelle d'Argy Smith, former editor of Cosmopolitan magazine, said: "Fashion is completely democratic and interchangeable now. You don't have to buy hideously expensive accessories to look classy and that goes for clothes as well. I just bought a pair of £90 boots from Schoon on Marylebone High Street and they look staggeringly expensive. There has definitely been a revolution in clothes. It used to be about how much money you had. Now it's just about what looks good on you, and that's fantastic."

Suddenly, there's a cachet to wearing cheap clothes - an idea unthinkable a few years ago. Women who would rather have died than admit they'd even been in Asda, Tesco or Primark eagerly show off their George prom skirt, Florence + Fred chiffon goddess dress or Primark military jacket, and exclaim "it was only £20".

But what of the designers themselves? Surely it's a bad idea to water down your creations for mass consumption? That may have been the case once, but because the chain stores are gazumping couture designs, it's a case of "if you can't beat 'em, join 'em". Stella McCartney's own range - think upwards of £800 for a jacket - sells to a few very affluent women. With H&M she's reaching an enormous young audience who may in time graduate to her main collection as their earning power grows.

She's not alone. Karl Lagerfeld went before her at H&M. Jean Paul Gaultier works for the French mainstream catalogue La Redoute, Luella Bartley for New Look, Bella Freud at Miss Selfridge. There's no perceptible loss of kudos for the designers. Liz Thody, fashion director of Easy Living, says: "It's good for the designer and for the store. The high-end labels don't suffer from women shopping around. Louis Vuitton, Dior, Chloé and Chanel have all seen their profits rise recently. The fast-tracking of trends from catwalk to high street has been going on for a while now, so why shouldn't the designers do it themselves?"

For H&M, recruiting a name such as McCartney pays massive dividends. It has placed the store at the top of the must-visit list for fashion-conscious women, a position it shares with Topshop (who got there first), Zara and even Debenhams. Thody points to the "championing" relationship that Vogue enjoys with Topshop. "This is not a passing trend. I think it's a result of what's possible in production values at high volumes. Clothes are better-made now."

She picks out the denim jacket from the McCartney range as a case in point. "But even though they're well made, clothes that last are not what anyone wants any more. Marks and Spencer should stop worrying about bullet-proofing their pieces and concentrate on the design." M&S, whose fortunes have been more closely followed than possibly any other brand, does not employ Paris/New York/Milan designers. The anonymous folk who churn out their shirtwaisters and slacks keep a low profile.

The only real "name" now at M&S is George Davies. The founder of Nextmay not have catwalk kudos, but his business nous and eye for a trend goes down well withM&S customers. They may even gain the store a lasting fan base which the quick hit of a McCartney or Lagerfeld cannot achieve.

As Thody points out, the quality of the H&M merchandise does not match the name on the label. No one would expect a £59.99 jacket to last for ever. The Prada wool coat you saved months for will still be going strong, both in design and quality, in 2007; the Zara cotton coat with this-season ruffles and frogging is already starting to look tired.

What no one talks about is where, and how, the clothes are produced. That's just not a fashionable topic of conversation. Meanwhile the style cycle spins exceedingly fast: on Friday more than 500 pieces from the H&M range were being offered on eBay - with few takers. The last two days have seen plenty of panic-bought items being returned to the store. But those discerning women in their thirties and trend-hungry teenagers are already asking, who will H&M get next?

'I wore £30 cardigan to award show'

Alexandra Shulman: Editor of 'VOGUE'

"My wardrobe is full of designer and high-street fashion. I recently bought and wore a £29.99 Warehouse cardigan to present a British Fashion Award and it was great. The simple reason that people can dress fantastically on a budget is that there is more and more good high-street fashion around. As editor of Vogue, I have a big wardrobe. And like Vogue, I like to mix designer and high-street clothes. A £770 black lace dress by Miu Miu, bought from Harvey Nichols, is great for parties. But you can also wear an £80 blue silk blouse from Fenwick. I think it's fantastic that Stella's H&M clothing range has had such a great reception. It's good for all ends of the market.

Lisa Markwell is features editor of 'Easy Living' magazine