I have a similar problem on mine but i dont get any hot water, ive been tols its due to having hard water where i live??? and British Gas suggest i get a new one, Ha ha, anyway what i did find out that at the top of the boiler there is a aluminum plate beneath that is some sort of swith i think, whenever my heating dosnt come on i give it a tap and it comes on, i dont know wht this unit is called.Hope it helps at least till summer
Joe., December 2006