Thanks Reg,
in the mean time I have seen this on Servonaut's page.
http://www.servonaut.de/shop/product...gm42u1425.html
The only problem is the Servonaut has an 8mm output shaft and I can't find a carden joint to suit the 8mm to 4mm shaft sizes
I will have another drive to the hardware store today and have a look at the range and sizes of the 12v drills.
Paul