I have an ideal Classic Combi FF 280 boiler, and today I tried using the central heating for the first time since the spring. However, it didn't work. The boiler does heat up the water, but not the heating. There is a switch for HW or HW + CH, which is turned onto HW + CH (and has been all summer). There is also a red light which should be on if the CH is on, but this is off, even though the switch is turned to HW + CH. Any ideas as to how to get the heating to work?