1. have you a room thermostat? may be turned down.
2. does the hot water light go out when hot tap turned off? if not, micro switch or h/w differential valve could be faulty.
3. check pressure on the dial. should be up to 1.5 bar with boiler turned off.
4. could be several other things as well. if none of th above, get someone in.
corgi 110, January 2010