The other option is the old lipstick in the fuel tank one!! (my favourite) The lipstick disolves in the fuel tank but solidifies in the fuel lines!! Costly little problem to find and fix!! I know, I have a nasty mind.....
Also, Campbell, where did you get the wheels as I had to wait 2 months for my 18's in the same Koya's. And have you scratched them yet?? 2 weeks and mine are buggered. The inlay is soft as butter!!