cheers for the quick response mate!
ive just done a quick search on cousinsuk and have found the following:
Sliding Gear Mounted ( 8120 ), Valjoux 7733 - £26.70
Minute Recording Runner, Mounted, 45 Minute, Height 7.22mm ( 8040 ), Valjoux 7734 - £24.95
Chronograph Runner, Mounted, Height 8.90mm ( 8000 ), Valjoux 7734 - £19.95
... PRICEY!
But i think that should do it yes?
Thanks again for your help!