There has been an almost endless array of Christmas parties this season, but it is doubtful that any of them had the grand style and creativity of the one Joe and Tricia Canzeri hosted in their Georgetown home Saturday. Canzeri, the longtime close associate of the late vice president Nelson Rockefeller and a former White House aide to President Reagan, is famous for not sparing the expenses to throw Christmas parties with a theme.

This being the year of the peaceful British invasion of Washington, the Canzeri home was decorated with such an evocation of England as to bring a lump to an Anglophile's throat. A heated tent in the back yard was turned into a British pub with wood beams, a dart board, a long bar, stuffed game animals and tartans on the wall. And the menu included suckling pig, roast venison, quail, spicy sausages and smoked salmon. The Canzeris even gave away a door prize, a $1,000, electrically driven, child's size Rolls-Royce, displayed in the pub resting on teacups. They were not Wedgwood cups, but no one complained. William Hart, who does President Reagan's daily news summary, won the door prize and now undoubtedly has dreams of the grandure of owning the real thing, with or without Wedgwood cups.

The evening did bring out an assortment of political colleagues and media stars such as CIA Director William Casey; Sens. John Warner and John Chafee; FBI Director William Webster; Margaret Heckler, ambassador-designate to Ireland; Ambassadors Rinaldo Petrignani and Allan Gotlieb and his wife Sondra; Republican National Committee Chairman Frank Fahrenkopf Jr.; counsel to the president Fred Fielding; television reporters Ann Compton, Lesley Stahl and Bill Plante; and TV personality Charlie Rose. The Reagan Library

There was another gathering Saturday night, one that brought together the president, the vice president and several past and present administration heavies to celebrate the start of an effort to establish the Ronald Reagan Presidential Library and Center for Public Affairs. The library is to be at Stanford University in Palo Alto, Calif., and the center in the San Francisco area. The glittery black-tie event at the Ritz-Carlton hotel brought 180 friends of the president to hear him explain that the library "will not tell the story of one man's presidency, but the story of a people -- a good and generous people."

In addition to President Reagan and his wife Nancy, guests at the dinner included Vice President George Bush and his wife Barbara, and former attorney general William French Smith and his wife Jean. Smith is a member of the six-man board of trustees for the foundation that will raise the money for the library. The other members of the board there were Attorney General Edwin Meese III, former Reagan aide Mike Deaver, former national security adviser William Clark, Hoover Institute head Glen Campbell, and former chairman of the Council of Economic Advisers Martin Anderson. End Notes

Six-foot-tall Danish model Brigitte Nielsen, 22, wrote a fan letter to Sylvester "Rambo/Rocky" Stallone, 39, with a photograph, and look what it accomplished. Yesterday the striking, statuesque Nielsen married the actor who made sweaty muscle a box-office commodity, at the Beverly Hills, Calif., home of "Rocky" coproducer Irwin Winkler. Fan-letter hopefuls should be advised that it helps if the writer looks like Nielsen. It also helps if the fan letter and necessary photograph are sent to an actor who's into narcissism . . .

Former senator Paul Tsongas, who retired after he was diagnosed as suffering from a mild form of cancer, was admitted to the Dana-Farber Center Institute after coming down with the flu. His family said Friday that he was in good condition and a hospital spokesman would not discuss the 44-year-old Massachusetts Democrat's condition . . .

People magazine's upcoming issue lists National Cancer Institute Dr. Steven Rosenberg, "who found a way to use the body's immune system to combat cancer," and Joseph Kennedy, 33, the son of the late senator Robert Kennedy who has decided to run for Congress, on its list of the "25 Intriguing People of 1985." Kennedy has announced he will run for the congressional seat once held by his uncle John F. Kennedy and now being vacated by Speaker Tip O'Neill. Others on the strangely mixed list include singer Madonna, the late actor Rock Hudson, former Nazi "Angel of Death" Joseph Mengele and empire-building publisher Rupert Murdoch. And what list could possibly be complete without Princess Diana and William (The Refrigerator) Perry? . . .