HDDP, Woody's spot on with that diagram. Woody, I do have the return spring... the problem is that the bit that it attaches to on the pedal box has snapped off, so I need a new pedal box if I'm to put the return spring back on.

So I guess I need to know... do I really need this spring? And if so, how much time would it take to replace the pedal box?

Thanks for the info re the Dronsfield Mercedes, I'll store that away and hope I never need to call them for parts!

Cheers guys.