I hope someone might be able to help. I guess the title sums up the problem pretty well.
The boiler fires up fine for both CH and HW but usually cuts out either before the rads or HW are warm enough or sometimes it will get the rads hot but then not fire again once they have cooled and allowed the room temp to fall below the thermostat temp.
It also sometimes fails to get the HW warm enough.
The timer control is telling the system be on and the room therm is at about 21 so it should be firing.
Boiler is a British Gas F2.
Any help/advice gratefully received. Thanks.