In reply to sleavesley:
Cheers for that, sorry for not getting back to you sooner.
Went for a cycle cross cause
A: Thought it looked purty.
and
B: I've always had MTB's so figured I'd wreck a dedicated roadbike frame pretty quickly by playing too rough.
Your numbers are pretty spot on as well but as I say I'm finding that the gears are running out of steam before me, though that's usually on downhills.
Ultimately though I'm either looking at replacing the whole system (front sprocket, rear cassette, chain) or getting myself another toy. I know the golden number is N+1 but can't really justify a third bike, no bloody space for it for a start...
As for top speed, not going to be happy till I crack 50!!!