Fanny - This is the word for a woman's front bits! One doesn't normally talk about anyone's fanny as it is a bit rude. You certainly don't have a fanny pack, or smack people on their fannys - you would get arrested for that! Careful use of this word in the UK is advised!
Give us a bell - This simply means call me. You often hear people use the word "us" to mean "me".
Hash - The thing you call a pound sign! Before you ask, yes it is also something you smoke - see wacky backy. Also to make a real hash of something means you really screwed it up.
I'm easy - This expression means I don't care or it's all the same to me. Not to be confused with how easy it is to lure the person into bed!
Jimmy - Actually short for Jimmy Riddle. i.e. I'm off for a Jimmy Riddle. This is Cockney rhyming slang for piddle!
Knackered - The morning after twenty pints and the curry, you'd probably feel knackered. Another way to describe it is to say you feel shagged. Basically worn out, good for nothing, tired out, knackered.
Leg it - This is a way of saying run or run for it. Usually said by kids having just been caught doing something naughty. Well it was when I was a kid!
Mate - Most chaps like to go to the pub with their mates. Mate means friend or chum.
Nicked - Something that has been stolen has been nicked. Also, when a copper catches a burglar red handed he might say "you've been nicked"!
On the piss - If you are out on the piss, it means you are out to get drunk, or to get pissed.
Pants - actually underwear... whole new meaning to cant find my pants
Quid - A pound in money is called a quid. It is the equivalent to the buck or clam in America. A five pound note is called a fiver and a ten pound note is called a tenner.
Row - Rhymes with "cow" this means an argument. You might hear your Mum having a row with your Dad, or your neighbours might be rowing so loud you can hear them!
Slag - To slag someone off, is to bad mouth them in a nasty way. Usually to their face.
Taking the mickey - See taking the piss. Variations include "taking the mick" and "taking the Michael".
U - A letter used far more in British. It is in words like colour, favour, labour etc. I think this is why UK keyboards have 102 characters on them instead of your 101, or is it because they have a pound sign on them?
Willy - Another word for penis. It is the word many young boys are taught as it is a nicer word than most of the alternatives. Some people also use it for girls as there are no nice alternatives. Hence "woman's willy". Also used by grown ups who don't wish to offend (this word is safe to use with elderly Grandparents).
Zed - The last letter of the alphabet. The English hate saying zee and only relent with names such as ZZ Top (Zed Zed Top does sound a bit stupid!).