There is a metal supermarket in Manchester, they have been reasonable on small orders, and if you nice the MIGHT chop it up on there kit for less than they really should.
Also in Liverpool (near where audi have moved to now) there is a metal merchant who does small orders to general public, not used them yet though. Name starts with an A I think... aww crap I went past there last week....bugger. I'll try and find out though.