My favourite is "pants" when something is awful. This single word led me and about five friends into a bizarre game for about two hours of silliness, where you change a single word in the title of a movie, book or song to "pants". Even a catchphrase is livened up doing this. For example: May the Pants be with you! Clear and Present Pants (hee hee!)
Another favourite is: B*ggery F*ck! (Thanks to Stephen Fry for that one.) And pretty much any expletive that emits from Hugh Grant's mouth (see the Blooper reel on Two Week's Notice DVD)... he's really inventive!
Other favs - shattered, knackered, dog's bollocks, "U wot?"
Slapper! (Love that one!) Cow (as an insult), and "dirty stop-out" when someone doesn't come home one night!
Of course, I try to say any of these, and they just sound stupid coming out of my mouth! :'(
The one thing I hate about Brit speak is the way they define time. I am so used to listing Month, Day, Year that I get confused when somebody talks in Day Month Year.... Or trying to plan something for the weekend. My husband and I have to stand next to a calendar and point to the day in question, just to make sure we understand each other. (Say if it's Wednesday, and I want to plan for the Saturday coming, I'll say "This Saturday", and he'll say "next Saturday!" Which to me is the Saturday a week away! Then the confusion and frustration.... ARGH!)
Ah, when language becomes an impediment to communication and understanding.... *sigh*
Morgana
ps - I hate "boot" for trunk and "bonnet" for hood on a car. It's my friggin' car and I'll name the bits the way I want!!!