My Potterton Gold Combi HE28 is misbehaving. I have it set to hot water only, but when I turn on a tap it makes a banging noise and the radiators start to get hot. I do get some hot water from the taps, but it's not right. Could it be a faulty diverter valve? Or could it be that the plate HE is partially blocked, and the divertor valve is opening up to the radiator feed under the pressure? As I understand it, it's designed to work the other way round, such that the plate HE acts as a bypass for the heating.