End casings as in those of the motor? I forgot to say that I'd already done that and poked around, mostly becuase I first suspected I might have driven the mounting screws too far in and into the windings. Didn't see any visual damage and the insulation on the windings seemed good as far as my rubbish multimeter could tell.
It's a shame I'm not so friendly any more with the electrician I used to know.
I've just tested the voltage between the case and ground and was getting barely anything readable on this cheap analogue multi meter. In 50, 250, and 500 modes the needle moved about the same tiny amount. I don't trust this meter much at all but I took a reading of mains voltage direct to test it and it read at about 240, or at least the needle went over to the high end of the scale.