I'm Northern British with hints of furrin travel:
I think this is 95% YART but heregoes:

vallay (but a car is valetted)
fillet (I never could never bring myself to order a fish thingy in McDonalds as I'm sure that they want me to say "filley of fish" which sounds to me like a young female horse)
markwis, a marquee is a big tent
herb - as Eddie Izzard said "pronounced with an "h" at the the beginning because there is an "h" at the beginning"

Didn't someone (maybe Rubrick?) have the view that words that were anglicised more than a hundred year's ago (like fillet) generally stayed the same in British English. Words that were adopted more recently tended not to be anglicised. I was wondering if we'd always kept expressions such as fau paux and deja voux in their native language.

By the way Mav, I'm definitely non-U
I have been heard to say "serviette" rather than "napkin"
Four-head - not forrid
Hankerchief not hankerchiff

Here's a quote from an article by William Livingstone for those who missed previous U-NonU discussions:

Professor Ross labeled certain pronunciations as U (for upper class) or Non-U (for not upper class). For example, U-speakers pronounce the word "forehead" to rhyme with "torrid." Only the Non-U would pronounce it as "four-head." Similarly in U-speech the last syllable of the word "handkerchief" is pronounced to rhyme with "stiff," and pronouncing it to rhyme with "beef" would reveal the speaker’s lowly Non-U origins.

Certain vocabulary choices also served as class markers at mid-century in England. Upper-class speakers called a dinner napkin a "napkin," but insecure lower or middle-class speakers who wished to move up a rung or two on the social ladder might choose a fancier word and call it a "serviette."

Although I’ve never heard an American utter the word "serviette," the same kind of linguistic social climbing exists in the United States. It was described (and condemned) by Paul Fussell in his book Class (1983), subtitled "A Guide Through the American Status System." Fussell wrote of the fondness of middle-class Americans for euphemisms and for polysyllabic words that "assist social yearnings toward pomposity." They say "gratuity" instead of "tip" and "pass away" instead of "die." In the speech of such people "selling" becomes "retailing," which then becomes "merchandising." They expect extra social credit for saying "utilize" instead of "use," for "medication" instead of "medicine," for "purchase" instead of "buy," and especially for saying "individuals" instead of "people."

http://www.texaco.com/support/opera/docs/speak0400.html

Aside: On the subject of cultural differences, rather bigger than herb and 'erb here's an interesting article that I found for Dr Bill, while searching for U and non U. It is a subject that I only learnt about recently while playing a game of Trivial Pursuit. The question was "what proportion of North Americans were circumcised in 1998?". We guessed at 5% of males (or whatever the proportion of those religions for which it is prefered and were more than astounded that the result was 80% (especially since 52% would have been female, I assume that the editors (where are they?) missed this small fact).http://www.cirp.org/library/general/morgan/