THE BRITISH, despite their worldwide reputation as prigs, love saucy knickers humor -- butlers dropping trousers, waitresses with weighty cleavage, judges who wear women's clothing behind closed doors . . . The naughty-naughty genre is as traditional as kabuki. How else do you explain Benny Hill?

Riffling through all the same undergarments is "Personal Services," directed charismatically by Monty Pythonite Terry Jones. It's loosely based on the story of Cynthia Payne, who was busted for running a classy, chummy, teas-on-Thursdays London brothel. After her much-covered trial, she became a British household name. And a consultant for this movie.

An effervescent and adept Julie Walters plays Christine Painter, a waitress forced into "the life" to pay the rent. It starts when her Greek landlord demands the rent either in cash or, as they say, in slap 'n' tickle.

Afterward, instead of revulsion she feels sympathy for her landlord -- and all the Dirty Old Men of the world. With her combination of graciousness and appreciation for life's ironies, she soon develops into a wise-talking, matronly libido broker.

In partnership with a hooker friend (Shirley Stelfox) and a former wing commander (Alec McCowen) who likes to dress frilly, she opens a sunshiny home for eccentric and depraved barristers, doctors, Air Force officers, politicians and other respected upper-crusters. Life at Cynthia's becomes one big party. Eventually, there's a raid, but the accused find themselves before a very familiar-looking judge.

Jones, who directed most of the Python films and took every opportunity himself to dress in women's clothing in sketches, directs this La Dolly Vita with wit and warmth. But this film becomes very much like one of its own parties. You can leave well before the end without missing much, except maybe some more underwear. -- Desson Howe. PERSONAL SERVICES (R) -- At the West End.