Doddy, good idea re the power supply. Doing that wouldn't create any risks of earthing loops would it? I only ask cos I had a nightmare when I first built this kit with steppers twiddling randomly while I watched. Turned out to be entirely due to my ignorance in that I thought I was doing a better job by earthing both ends of the shielding on the stepper cables
Edit: bugger. Power supply is 27V, just enough to exceed 24V max for UC400!