hi after returning from christmas hols last week,my boiler had no pressure and flame failure light was flashing.i pressurised the unit and reset it and the heating and hot water worked fine.came home from work today to no heating and the flame failure neon was flashing again but the pressure was ok.reset and have heating and water once more.has anyone any ideas to what the problem may be?i now notice it seems every time the heating is suposed to come on with the timer i get the flame failure neon and have to reset to get the heating to work and also hw doesnt seem to get as hot.