Common British Slang Words and Terminology

Ace - If something is ace it is awesome. I used to hear it a lot in Liverpool. Kids thought all cool stuff was ace, or brill.
Aggro - Short for aggravation, it's the sort of thing you might expect at a football match. In other words - trouble! There is sometimes aggro in the cities after the pubs shut!
All right? - This is used a lot around London and the south to mean, "Hello, how are you"? You would say it to a complete stranger or someone you knew. The normal response would be for them to say "All right"? back to you. It is said as a question. Sometimes it might get expanded to "all right mate"? Mostly used by blue collar workers but also common among younger people.
Anti-clockwise - The first time I said that something had gone anti-clockwise to someone in Texas I got this very funny look. It simply means counter-clockwise but must sound really strange to you chaps! I think he thought I had something against clocks!
Any road - Up north (where they talk funny!!) instead of saying anyway, they say "any road"! Weird huh?
Arse - This is a word that doesn't seem to exist in America. It basically means the same as ass, but is much ruder. It is used in phrases like "pain in the arse" (a nuisance) or I "can't be arsed" (I can't be bothered) or you might hear something was "a half arsed attempt" meaning that it was not done properly.
Arse about face - This means you are doing something back to front.