Right, I turned my heating on and realised that my downstairs radiators were ice cold but my upstairs ones were red hot. I checked my pump in the cylinder cupboard (danfoss pump) to see if it was spinning by removing the large screw cover to see the impeller spinning. It was running fine. I turned the room stat down whilst I fiddled with a few locksheild valves to see if I could force water through the downstairs rads. When I turned the room stat back up the fan was running on the boiler but it wouldn't fire. This happened a couple of times. I noticed that the over heat switch was in the "out" position so I pushed it back in. ( the boiler is a glow worm ultimate, unsure how old) the boiler fired up temporarily but not for long. Now the fan doesn't run or boiler fire when the room stat is turned up or when I open a hot tap. I have two motorised valves in the ac cupboard if that helps. The pump is now constantly running and only stops when i switch off the power. What could be wrong??? Thanks.