wrote:
I'm not a plumber or heating engineer, but when we recently had boiler
problems (cutting out), it was caused by a failing water pump. We
replaced the pump, and everything was back to normal.

Hi thanks for the reply. Can you remember if the pump was still making
any noise as if it was working fine?

Well in fact the opposite. On close inspection of the pump there was a
distinct lack of noise, and the casing was blisteringly hot. It was
pretty clear that it wasn't functioning correctly.