I think the motor might be at fault, see diagram. For the tests I did, I disconnected the connector 'spades' from the carbon brushes. There should be some way to apply a differential voltage across those spades, and there is not. Looking closely I'd say the internal black lead that ties to spade B1 (I named the brush on the same side as the connector "B1") looks a bit heat stressed.
To review: The machine tripped a circuit breaker in the consumer unit, (and there is some discolouration at one of the mains input tabs on the PCB). So at that time I assume a fault current, possibly a heavy current, was flowing. I'm not sure if it would be L-N or 'earth fault', or one leading to another?
My "wild guess" is the internal connector.pin5-to-brush-spade leadout has melted / 'fused' (is that plausible?) maybe if I run a wire direct to spade B1 the motor might work. However, if the internal black wire lead-out to brush B1 has some inaccessible "last-gasp" fuse, it'd be wrong just to bypass it.
It'd be nice to know of a place doing reconditioned motors, as they cost £200 new.