Hi
Just use the part number CEN wrote in his replay under CEN website and contact any dealer. I have had good luck with http://www.offshoreelectrics.com/.
Just e-mail them and give them the part number and he will get it for you if it's in stock at CEN Racing.
No I do not think you have to buy spare parts from the US just use the spare part number for the engine in the UK and you should get the right parts. But i'm not sure.

I hope I have cleared something out for you.

Magnus
Sweden