"Those with it (money) always seem to have it," says Bill Gibbs about his "dash with cash" customers, as he calls them, borrowing the phrase from Vogue magazine.

Like other designers of fantasy clothes - and Gibb and Zandra Rhodes are the best of them - their business is booming in London. There are currently 1.3 million unemployed in Britain, inflation is running at a rate of 16 per cent at this moment, there has been a drop in the standard of living and the value of the pound has fallen off considerably, particularly against the dollar.

But in spite of this, or perhaps partly because of it. London's designers of fantasy clothes are getting bigger orders from stores and private companies in America and elsewhere (though not yet Washington) than ever before.

"I always wanted to be a costume designer," says Gibb. "What comes out is always fantasy."

Even when he start with the most traditional fabrics, fantasy clothes result. What could be more classic than tartan, and he uses the authentic variety. But when he adds a border of tapestry to the hem of a plaid skirt and teams that with a silver embroidered black velvet jacker, the result is hardly the garden variety tartan outfit.

The same goes for paisley or tweed. They never tame his extravagent designs.

He's more extravagant still in evening wear for client-friends like Elizabeth Taylor or Petula Clark, Twiggy, or the Begum Aga Khan.

There is a hand-printed satin kimono-style coat over Lurex knit top and knickers, with long tassles. The shapes are unrestrained when he used printed lame, net and gold lace. What he calls a "quiet dress" is silver lace with a large cape collar.

At the moment he's watching carefully what is selling in his Bond Street shop. Should he see a tendency to very understated, classic clothes, he'll give them a try.

But it is not likely they would end up looking very classic.

Zandra Rhodes is a fabric designer whose fantasy clothes often take off from the fabric pattern itself. Last year it was castus prints inspired by her trip through Arizona and New Mexico. This year she has been to Mexico (which she didn't like much but there are new Mexican brick prints along with the cactus.

"It's like painting with numbers," says Rhodes, pushing back her dyed, grass green bangs. "I cut out around the pattern (in the fabric) to whatever form it takes."

For starters, the shape of her clothes includes a basic top seller in the line, a long-sleeve shirtdress style with fullness springing from soft pleasts at the base of the finely pleated collar. Those pleats are carried from crepe into chiffon and are never bothered by - in fact, usually enhance - the patterns. The new "basic" style has wide sleeves and while the belt is optional, Rhodes prefers it worn that way.

Mohair knits are new and true to Rhodes, in full blown cocoon or balloon shapes. Quilting is used more frequently than ever, for skinny pants or for coats. One handrolled chiffon dress in banana leaf print has fabric cascaded from a yoke of quilted satin.

She has put crinolines under several organza styles for women who go to extravagant parties aclling for such garb, but is quick to add that these crinolines can be removed, "and the dresses become perfectly nice styles to wear to dinners at home,"

Rhodes has not been at King's Road, but she has heard about the punk rock crowd among London's teenagers, who decorate themselves with safety pins and bathroom chains in a successful bid to be "different." Her fabric design assistant is "one of them" she says. In response to this movement she's made a group of dresses decorated with sequinned safety pins and dry-cleanable hardware store chains. Integrated into the design of the clothes are what appear to be unintentional rips but which are, in fact, well planned and always the same in each style of dress. "Everyone who has seen them has loved them," Rhodes says gleefully.