Hi - the mains light is on all the time ( well maybe not at midnight) and it never used to be. The orange light used to go on, the boiler would fire up, then after it had stopped firing, the main power light would go out too. Now it stays on. Eg, heating actually switched off timer at 8pm tonight but power light is still showing lit - and it’s 9.30pm. Heating engineer changed a valve (?) before Christmas and it seemed to be OK for a few weeks, but now the light is back on most of the time. I can hear something running in the boiler but nothing should be operating, ie it should be shut down for the night. I know nothing about his kind of thing but it’s like there is excess heat in the system that it’s trying to get rid of. We have underfloor heating if that’s of any matter. It’s an oil only boiler, pressurised system. Any thoughts? Thanks.