Bare in mind that a US keyboard has a different physical layout, so you can't just take a US keyboard and swap keycaps and have a UK keyboard. Here's a US one for reference -
Due to the way that a Model M is designed, it is possible to take a US one and convert it to be a UK one, but this involves quite a bit of work - see
this for an idea of what you're up against.
Dunno about you, but learning the US layout would be easier to me =P