what's wrong with "can i bum a fag?" (except that i don't smoke...) Usually it would be "you don't mind if i bum a fag off of you?" you wouldn't usually say you were bumming a fag just on its own.
you don't say 'dodgy'? what sort of a society are you running over there? WEIRDOS!!!
drawers is another good name for pants, do you use that in north-americaland?
there are so many that i myself have to watch, coming as i do from orkney, that even the rest of the UK don't know about. I had to stop saying 'peedie' when i moved away from orkney (it means small and is only used within orkney, shetlanders say 'peerie' to mean the same thing) for example and there are a ton more...