Please help!! I have a potterton suprima 60 and it keeps cutting out. When i put the hot water on with the switch upstairs the boiler does nothing so i have to go down stairs switch the boiler off on the isolation switch and the boiler starts up and every thing is fine for about 2 minutes, but then the red light comes on and the boiler just stops working. If i turn it off again at the isolator it starts up again then does excatly the same thing. its driving me mad