LONDON, Jan. 21 — Only one small mischance marred an otherwise sparkling production Saturday of the wedding of American screen and stage actress Sharon Tate to Polish film director Roman Polanski:

When the bride and groom came to cut the cake at their Playboy Club reception, the frosting on top read “Happy Retirement, Hilda.” The busy bunnies had brought the wrong cake.

“We don’t mind, if Hilda doesn’t,” said Sharon.

The reception proceeded with such guests as Michael Caine, Laurence Harvey, Leslie Caron, Warren Beattie, the Anthony Newleys and Candice Bergen.

Among the invited who were unable to attend was Princess Lee Radziwill, a friend of Polanski.

Hilda, whoever she may be, didn’t turn up, either.

Sharon, starring in “Valley of the Dolls,” wore a green silk, mini dress and flowers in her hair for the wedding at the Chelsea register office. Polanski also favored green, in a regency-style suit.

The couple met when Polanski directed Sharon in “The Vampire Killers.”

Said Miss Tate, 25, “Roman and I plan to stay in England for a week. Then we will fly to California for our real honeymoon.”