On Thu, 17 Dec 2020 08:13:52 +0000, Andy Burns wrote:

I've tested the solenoid resistance on the left with my cheapo
multimeter at it is showing open circuit , so has presumably
failed.
Are there any other checks I should do?.

Or is that pretty conclusive?

Sounds it.

High up the list that's for sure.

I don't know much about the gas valves, does the solenoid control
the
flow of gas to the pilot as well?

Mine's a permanent pilot, and yes the solenoid valve supplies it
(controlled by thermocouple) ...

This boiler doesn't have a permanent pilot. Logic/safety would
suggest that the gas for the pilot is not supplied without incoming
mains and the spark generator running (possibly with a time out).
Once the pilot lights it heats the thermocouple that operates the
main gas valve solenoid. Loss of mains causes the main and pilot gas
valves to close shutting of the boiler and pilot.

In theory... See if the service manula can be found on the 'net to
find out how/what it is supposed to be doing.

--
Cheers
Dave.