It is, as they say, London's year to howl. After a wildly successful showing of spring fashion collections here, Vogue has been left gasping ''Youthquake,'' while Women's Wear Daily cooed ''fashion passion in the English capital.'' Suddenly, after several years of post-Vivienne Westwood sartorial decline, London has once again picked up the thread of world fashion leadership.
For years no one had pretended that the English were particularly adept at marketing their potpourri of cutting-edge clothes. Indeed, what else prompted The (London) Times fashion editor to write in a fit of pique, ''The British prefer to wear their fashions than sell them.'' Oh, there had always been lots of chatter about London's ''creative energy'' and proverbial street fashion, of which the '60s were the recognized acme. But the country remained caught between its energetic, youthful design contingent and its large, staid textile manufacturers. The scene was further muddied by England's complex and unique tradition of style - a sense of understatement rooted in class consciousness and quality craftsmanship that has little to do with overt displays of status.
But now those in the fashion know - editors, buyers, and the like - are pointing to a new seriousness, a new businesslike attitude on the part of London's young designers, and a willingness on the part of the large manufacturers as well as the government to work with those designers to revitalize Britain's clothing industry.
It is this new crop of clothiers now coming of age in the rather somber wake of the Swinging '60s and Carnaby Street (remember the Mini and Twiggy, as if you could forget them) that has everyone in renewed paroxysms over England's impact on global fashion. Many American buyers found London a ''must see'' on this year's whirlwind round of fashion shows. British Fashion Council chairman Cyril Kern says that orders for the 1984 spring collection eclipsed those of any other year except for the bench-mark '60s.
''It's a combination of both the climate and the fact that standards have improved,'' says Michael Rosen, a senior lecturer at London's Middlesex Polytechnic, one of the leading fashion schools in the country. ''Two years ago it was the Japanese, then it was the Italians. Now it's right for London. But we also have more designers here now, and the emphasis on marketing is different. A lot of designers are interested in the whole concept - accessories and licensing - rather than just doing a dress and hoping the Princess of Wales will wear it.''
The renewed flirtation with London's sartorial best and brightest began about two years ago when the Princess of Wales became the most popular cover girl. It carried into international renown such previously provincial designers as David and Elizabeth Emmanuel, Jasper Conran, and Caroline Charles. All hailed the ''New Romance.'' And it was indeed a coup for Britain's upper middle class, the so-called ''Sloane Rangers'' that were generally seen as frumpy dressers and out of touch with the Punk Revolution occurring on the streets.
But since then the other end of the sociocultural scale has also come into its own. And such names as Katherine Hamnett, Stevie Stewart and David Holah, and Robin Archer are also earning international plaudits for their streetwise New Wave designs that collectively move American sweat shirt clothing into the realm of designer chic. ''The English are reserved on the surface but wacky underneath - that's what our clothes are,'' explains Ms. Stewart. Today London fashion is a two-pronged trend that has little to do with the devil-may-care look of ''punk'' that still strikes Americans as avant-garde but no longer raises even an eyebrow on Kings Road.
''Punk used to turn lots of heads,'' says one young designer, ''but now everybody is a punk.'' Some observers have even gone so far as to label the new London mood a respectable if dull ''back to basics'' move. There certainly is a lot of talk about quality workmanship and professional business practices.
''It's just a lot of hard work,'' explains Ms. Stewart, one-half of the successful design team ''Body Map,'' whose signature clothes are long, lean, layered, and available in three colors only - cream, white, and black. ''It is true that we (Britons) would rather wear our fashions than sell them; that's why so many English designers have been stuck on one level for so long. But we are trying to go beyond that. We're so determined.''
''Britain's been streaks behind,'' adds patrician-looking Arabella Pollen, one of the New Romance contingent sitting comfortably in her sun-washed design studio in southwest London. ''Our street fashion has always been the best in the world, but other than that we've been considered slightly a joke. We've had no money, our presentations have been bad. But this year people have started getting serious.''
''Fashion is very natural to young English people; it has been ever since the '60s,'' says Katherine Hamnett, a leader in the avant-garde group whose eclectic collection of wash-and-wear clothes sells well on both sides of the Atlantic. ''We're quite a poor country now . . . with lots of bad weather, and people can feel cornered. So (designing) is a natural way to express your individuality. I wore a uniform at school for years, and that's enough to make anybody a designer.''
''I think New York is a far more creative place than London,'' says Mr. Rosen , ''but for some reason it's easier in the U.K. to be a viable young designer. You can be 18 or 20 years old and have your own design business. In the US there isn't this nucleus of young designers.''
''Life in the U.K. is very difficult for young people,'' adds Mr. Kern. ''(The new designers) have to try harder. At the same time they are looking to the US as an example (of successful fashion merchandising).''
''I want to get into this American idea of franchising,'' says Ms. Pollen, who, unlike most young designers, attracted a private investor early on. ''That is one of the things wrong with this country. The designers are very low key, they haven't taken the plunge. Really, you've got to be expanding all the time.''
Such enthusiasm is easily matched by Ms. Stewart, who, like many of her fellow designers, ventured abroad in search of postgraduate fashion experience. When Milan didn't appeal to her and her partner, David Holah, the duo returned ''really fired up to make it in Britain,'' she says with a shake of her head that sets her anchor-shaped earrings into motion. Body Map's spring collection, ''Olive Oil meets Querelle,'' features a sailor motif, bits of which the dark-haired designer is wearing.
''We went to the bank manager, and it was really hard to get a loan during the recession,'' she explains. ''But we did well in our sales last year and that helps.'' Ms. Stewart cites such new American clients as Macy's, Henri Bendel, and Bloomingdale's as proof of her company's growing success. ''America is very aware of young London,'' she says. ''But we don't want to outprice ourselves. We want to stay affordable to the people here.''