Last wash was OK. Next switch on and the blue LCD menu did not display anything. Power is available inside as it makes some "normal" noises. Anything I can try before I take the covers off to have a look?
I'm responding to my own question. Several hours after the posting (and before switching on) I moved the machine a few inches to recover a lost tool which had fallen down behind and when I switched on the display lit up. Either previous finger trouble at the controls needed time for an auto reset or a dry joint / bad contact was made good. Time will tell if it is permanently OK. Whatever ... if it aint broke!
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