So after a reset, a drive power cycle, and checking the settings again, I realised the phase fault detection is not activated as standard. Why you wouldn't enable all the fault detection options as default I'd love to know..

After activating it, the drive went straight into fault. Following a bit probing with the multimeter, and some tugging on wiring, I discovered one of the contact pins for the motor wiring had pushed out the main multiplug on the mill for connecting the control box. It pushed and locked back in, so I'm not sure how it had come out, but I now have movement, and the auto current loop configuration worked.

I'm sure I'll be back with more questions about the anti-resonance tuning, but that can wait until I have all axes working.