Looks like i have opened my big mouth before looking. I have looked in my box o stuff and cant see the speedo drive anywhere so im sorry i wont be able to help you after all.

not a problem thanks for looking
if you get desperate i,v got a spare g/box that could possibly be robbed ,
thanks Spanners i could be taking you up on that offer but
Think you've got a speedo drive fitted to your front wheel.
Not sure what ratio it is etc. but you were going to have to get the speedo re calibrated anyway. Might be worth doing a bit of maths, to see how far out it would be, if you use the bike drive and the Reliant speedo.
Or you could fit the correct speedo for the front wheel.
I do have a speedo drive in the front wheel i surpose a custom cable would get that going if i'm stuck,I think speedy cables can do both the recalibration and the cable