Thanks for all the info peeps. Have spoken to Keith and he does sound like a really helpful chap indeed. However, due to his obvious popularity he can't look at my bike for a few weeks and i need it for my work so gotta go else where! :-(

Rabb - the issue is that when the bike is idling it all sounds perfectly ok but as soon as i put it in gear and pull away i get a knocking noise coming from low down in the engine area (i can feel it knocking through the seat) and i'm worried that if i ride it it's going to bust more than it probably already is.