Thanks to both of you - after taking the top off the machine and delved
around near the safety interlock, I found a broken cable that was
supposed to go to one of the contacts on the safety interlock. The wire
was corroded and quite brittle for around 2 inches. I cut the wire back
to good cable, re made the joint with the spade connector and hey
presto, the thing works fine !!

This is my first go at using these newsgroups, but after the advice
I've received (and the money I've saved) it won't be the last!! 8-)