I have now taken delivery of the lathe. The SoP is as follows:
The lathe is virtually unused - it even has much of the red waxy preservative still on it. My suspicion is that it was in the hands of a beginner who abused it and blew the board first time of use; either that or he was just unlucky.
The accessories were missing - but I knew that.
The drip tray has been bent. I hadn't noticed that, but it is trivial.
I have reconnected the control board after having made one minor modification. The motor leads are fitted with female spade connectors, and these are pushed onto solder tabs on the "Forward-Off-Reverse" switch. This is a horrid bodge that doesn't work at all well, so I've soldered short flying leads onto the switch with female bullet connectors and fitted male bullets to the motor lead.
The symptoms:
A faint crackling sound when applying mains power.
The motor either fails to run and the "Fault" light illuminates.
OR
The motor runs at a constant speed regardless of the position of the speed controller. I would estimate that it is running at about half full speed.
THEN
I disconnected the motor and mains leads prior to removing the control board for the purposes of changing the output drivers.
I wanted to check something and reconnected the mains and motor. One of the mains spade connectors felt a bit dodgy so I tweaked it a bit.
Plugged back into mains, and LO! a miracle had occurred - no crackling noise and it works perfectly.
I'm going to carefully inspect the underside of the controller board for dodgy solder joints just in case, but otherwise I now seem to have another nearly new working mini-lathe.

The question now is whether to sell to fund other things, or keep as a spare / for parts.