Last season, fashion's nuclear family made obscene gestures as three generations gyrated down the runway in scruffy black overcoats, black leotards and bottom-length sweaters with knee-length sleeves.

This season, Grandma wears a printed taffeta court dress complete with full skirt, Mama wears twin frock coats and Daughter skips along in a long pink jersey gown, dyed to match the pink toilet paper she trails behind her. Or: It's clean-up, dress-up, shape-up time in London.

Punk and funk are giving way to pearls and petticoats. Buttons are replacing safety pins. And in the smart Soho clubs, the young wear black sweaters and black ski pants with Chanel gold chains and first-generation high heels.

The streets along Kings Road, where even some of France's most famous designers come for fashion inspiration, are a lesson in fashion sanitation. While there are still lilac-colored dreadlocks and spiky Mohawk hairdos to be found, the real spectacles of the moment are the round, tortoise-shell, lensless frames being worn by all the kids with 20/20 fashion vision. Some of the big looks of the moment include denim -- especially prefaded, preworn, pretorn, predecorated denim worn either as a total look or mixed with other fabrics.

Such establishment looks as pin-striped suits are now de rigueur along the boulevard of fashion outrage, and the newest accessories include hairpieces that range from pigtails to curly ringlets -- some of them painted on papier-ma che' wigs.

The thrust of London fashion seems to be moving from the streets to the salons, where designers now export 1.2 billion pounds worth of clothing annually. The one fall fashion item that seems to symbolize this move is black leather. Once the province of punk, it now appears in the most expensive clothes. If Bruce Oldfield continues to influence the princess of Wales' wardrobe as he has in the past, black leather may well turn up next fall on the back of the future queen of England.

Oldfield opened his show here with mink coats worn over textured black leather suits with fitted peplum jackets or mink jackets over slender, double-breasted black leather coat dresses. The look is right now more Joan Collins (an old Oldfield regular) than Princess Di, but with the princess' amazing grace at adapting new fashions to her own regal syle, the sharp and shapely black leather suit may yet make it to the royal wardrobe.

Like many designers this season, Oldfield uses pleats to express the new fullness in next fall's clothes. One standout is a pleated gold lame' jacket that shelters a gold lame' gown with fan-pleated skirt. The design most typifying what you might fantasize as a gown fit for a princess is Oldfield's maroon velvet gown that dips to the back, forming just the hint of a train. Its off-the-shoulder neckline is banded in mink.

The move from a more street-savvy layered look to a new kind of soigne'e that is being called "the new couture" is perhaps best exemplified by the collection of newcomer Alistair D. Blair.

With a design background that includes jobs at Dior, Givenchy and Chloe' in Paris, the young Scottish designer draws on couture to produce some of the most sophisticated clothes of the season. His long navy gabardine coat that stops about two inches above matching trousers is a sweeping tribute to his talent at handling volumes of fabric with a deft, sure hand. And his shocking pink cape over matching coat and short, knee-hovering skirt is a lesson in the wide-over-narrow, long-over-short look so prevalent in the Milan collections.

Like Oldfield, Blair endorses the full-skirted look in a silver lame' gown with turtleneck halter. The elongated waistline bursts into fullness at the hip and continues to just above the ankles. Blair's surprise touch for the evening: long gowns shown with knee-high leather boots. With fashion outrage out of fashion this season, the young designers who shocked their way into style seem to be in a state of shock, locked in the past, unable to move on to something new. Many have had frankly disappointing collections, and many American retailers are openly grumbling about the level of professionalism. This city, that was so long denied its just due as a fashion center, has now attracted the world to its feet -- only to trip over its own creativity. Or lack thereof.

There are exceptions. Rifat Ozbek, for example, who caused international fashion waves last season with his salute to Italian movie heroines of the '50s, draws inspiration this season from the ballet. He describes his new look at the barre as "half classic, based on men's outfits, not women's tutus, and half modern, based on Martha Graham."

The Graham part of the collection includes a remarkable group of simple, spare evening dresses with high necklines, long sleeves and skirts that flare gently to ballerina hemlines. All are made of heavy rayon crepe and are shown with Manolo Blahnik's stylized ballet slippers on heels. Ozbek's daytime clothes are equally lean and shapely, and they have the added dimension of comfort so lacking in the skintight clothes in Italy.

Ozbek built in comfort through his especially pretty rendition in black reembroidered lace conjures up memories of Audrey Hepburn in her "Sabrina" necklines and full skirts.

Katharine Hamnett, whose first fashion notices were for her message T-shirts, only has two instructions for fall: "Ban the Bomb" and "Vote." The woman whose causes have ranged from "Save the Whales" to "No Nukes" seems to be preoccupied now with sex. Her big messages now are sensuous, skintight bodysuits worn by models imitating James Bond's favorite sex kittens, and explicitly sexy denim shorts and jeans with back and side slits veiled in black fishnet.

Some of the models got so carried away that they looked as if they might have been demonstrating Dr. Ruth's therapeutic messages. Just when it looked like the vice squad might be called in, the show closed with three red shimmy dresses. They were worn by blond-wigged look-alikes of the Supremes who frugged down the runway to the "Talk-About-Love-Love-Love" music of Chain Reaction. The audience went wild.

They went wild, too, at Body Map, where the new fall look includes such bright ideas as rainbow-colored raincoats, pink tweed full-skirted dresses with ostrich boas, double-frocked coats of Tudor inspiration, and the one single item that seems to summarize the general cleanup of young British fashion: a "bondage" dress, all wrapped and knotted around the body -- not in bad-girl black leather, but in good-girl white jersey.