Lady Wright hastily disclaimed the opium pipe or the rare copy of "Confessions of an Opium Eater," props in the setting for Sherlock Holmes' Baker Street digs. "Oh dear, no," she said. "Next thing you know, someone will say we raise hashish -- pot -- in the garden."

With trees upstairs and holiday room settings downstairs at the Watergate Hotel, The Washington Home benefit, "Entertaining People With a British Twist," opened last night.

Marjory Wright, an honorary sponsor, admitted to owning the muffin dish. "I can't think how we'll do without it," she said. "It's the only one in the British Embassy," said Suzanne Gilligan, who worked with designer Anthony Browne on the setting.

Lady Wright had come to check the setting earlier yesterday, complained because there were no "pikelets," as she calls crumpets, and went back to the embassy to toast some. Browne admitted later that he's responsible for the missing bite.

The "treeview" (as Trish Saul, tree chairman, called it) opened The Washington Home benefit, which runs through Monday. About 225 people attended, paying $125 each, said Betty May, the buffet chairman. Chairman Jane Sloat said both Barbara Bush, the honorary chairman, and the British Embassy wives, headed by Lady Wright, had been volunteers at the Home for years.

A tree decorated for Bush was covered with red ribbons and cookies, each sanitarily encased in a plastic bag. "Those are our cookies," Bush asserted. "We've had a cookie tree for 40 years. Not that I still make them myself. I did for 30 years but now our wonderful Paula Readon does them and very well, too."

As for her husband's views of the summit, "What do you think he thinks about it?" she countered. And then she added, "I think it's wonderful!" Is she proud of Nancy Reagan's performance? "You bet!"

Bush found many familiar faces on a tree decorated with silver flowers centered with pictures of residents of The Washington Home, an upper Northwest nursing facility. The decorations were made by the residents and the British Embassy wives.

Solanges Vivens-Archer, nursing director, said the residents were still talking about the attention they had received from the press and the princess of Wales during her recent royal progression.

Eunice Shriver was surprised to find that the nursery setting she'd suggested to designer Theo Hayes was completely equipped with a (live) nanny, Patricia Lathan, and a (live) baby, Cathryn Minshall, 6-month-old daughter of Suzanne and Peter Minsall. The baby, who undoubtedly will grow up to be a star, gurgled, smiled, cooed and stole the show.

Alan and Dianne Kay's setting was done by Victor Shargai, who's also decorating Merrywood for them. The Kays, after paying Nancy and Wyatt Dickerson $4.25 million in July 1984 for Jackie Kennedy Onassis' childhood home, have spent a year and a half remodeling the house on the Potomac cliffs. "We plan to move in this February," said Kay. "We're planning 12 parties, all for different charitable groups."

Other than the baby, the most enthusiastic guest of the evening was Chloe, appointed by Nancy Reagan as the international mascot for the "Just Say No" club, a drug prevention promotion aimed at for small children. The Lhasa apso brought Christina Wachtmeister (the daughter of Swedish Ambassador Wilhelm Wachtmeister and the Countess Wachtmeister) as her date. Chloe, who wore a Christmas-red sweater and bandanna, normally is hostess at the Swedish Embassy, Christina Wachtmeister said. Rather than compete for attention with Chloe last night, Count and Countess Wachtmeister went to Tokyo.