Theo wrote:

I don't know if you can actually get the parts these days, or whether
they're sufficiently pattern that you can find or fashion suitable
replacements.

I've had to replace the thermocouple, obviously they're generic sostill
available, I think I have a spare somewhere, It has no electronics, if
the coil on the gas valve goes that might be curtains for it?

I'm guessing you don't have the gravity hot water as described, though?

I do.

It
sounds like that was a good reason to fit zone valves and controls on the
hot water, even if you kept the boiler.

it's sleeping dogs now ...