2 differences in english expressions between UK and North America:

In UK, to knock one up means to knock on their door to wake them up. In Canada it means to get someone prengant.

I had fun with that on while visiting UK with some Canadian friends I told a young lady we would come by in the morning to knock her up. Too bad I cant portray the looks on their faces across the Net.

In UK up yours is a drinking toast, I guess it is short for up your glass. Here, up yours is an insult, usually accompanied by a raised middle finger, and means you should insert something up your you-know-what.

You can have lots of fun with that one, but please be careful!