A neighbour has this combi boiler out of action with the overheat LED
coming on solid after a few seconds, and no fan spinning.

I deduced fan failure and narrowed it down to a faulty relay on the main
PCB. I've replaced that, and it's now got a running fan, pump, empty
condensate trap - but no ignition, absolutely no attempt at sparks and
no voltage at the gas valve.

Thinking something phutt has gone wrong with part of the PCB that drives
the ignition voltage generator, but then again it could be some
programmed line in the micro yelling 'If adrian is messing about with
me, just be as safe as possible'.

These neighbours haven't washed themselves in hot water for three days
and their dog looks a bit distressed....

I'm thinking I might soon be running in the direction of Geoff for a
recon PCB but is there anything else I've missed?

--
Adrian C