Hi Tom,
Not a very scientific reply I'm afraid, downloaded the earlier uploader and had a tweak with the pots,everything running fine now (in fact the Nema 14's are running quiet, fast and even cool/cold).
I found that on sending the mount to "home" the motors were noisy as hell, but a little tweak on the pots got them running quietly.
Another weird thing is, I checked the voltage from the ref point to ground, but all I could read was about 11.6vdc, but hey as I say all is up and running and connected to Stellarium after a few probs, cos I can't get on with CDC (too tceh for me, and I can't visualise what I'm seeing on screen)
Thanks for the great work and all the best for your future.
Rob.