When someone only learned to speak like having a hot potatoe in their mouth he would not get the fine nuances and differences in british slangs and accents. There are literally hundreds or even thousands different accents in the UK.
My favorite is northern Yorkshire. It sounds like a parrot who learnt speaking from a Scot and a Cockney together and got adopted by a Welsh who apparently already had another parrot swearing in lower german. :)

I like the australians "cactus". I think that has depth.

#21 It's: Aluminium remember the second i for proper British pronunciation ;-)

Knob head - I think that works fine in the US also

I really wish we used the word "c#nt" as casually as they do.

"Sommat" is a good one. Also, I like when they just say part of an idiom instead of the whole thing, like "snowball's chance" or "better late" or "apple-a-day and all that."

I would never shut up if I had a British accent

#21 it's aluminium you muppet. I can highly recommend everyone to watch some Jimmy Carr now is a proper nutter. absolutely magnificent.

Has anyone heard how they say respritory? They hit the spirit part very hard.