I know it's been done before, but I think that it bears repeating. (There may be a joke about bears eating unsavory campers in here somewhere...)
Anywho, I'm always keen to hear a word that I'm not too familiar with, or in a context that seems 'off' being spoken by someone from the UK. I'd have to say being spoken by someone from England, in particular, given that I'm here, in England, and most people I come into contact with are either English, or have come here from somewhere else and have adopted English English as the English to speak, if you know what I mean.
Here's a short list of words that I hear, but don't yet have the chutzpah to use:
punter: a paying customer, often used in association with hookers. (I visualize men kicking...)
knackered: tired, although I seem to think that it more often would be used for "very tired".
gobsmacked: shocked, astounded. (gob: mouth)
jack-the-lad: bad boy
gutted: saddened, upset (sounds too much like eviscerated, so, until I get over that, I don't think I'll be using it)
caf: slang for 'cafe'
telly: television (makes me think of 'telephone' when I hear it)
Words I hear and do use:
quid: used like the American term 'bucks' with respect to money.
salad: lettuce, tomato and the like that would go on a sandwich being made for you at a deli.
kilo: it's not just for coke anymore! (this would include any metric measurement)
Words that I thought I'd never hear here:
cheerio: I think that we all know what this means by now, right?
half-caste: this word was used by a fifty-year-old man to describe a person of mixed parentage. This term is certainly offensive back home. Is it not here, too?