Thanks. Very helpful. I have been fearing the economics of having the hot water on when I don't need it, but if it's not really doing anything then that's great to know. And probably more economical to have it kept warm than heating up from cold every morning.
I have a potterton ep2002. I have set the timer so that hw & ch come on once in the morning & once at night. I don't particularly want the hw on at night, no need to heat water for as long as heating is required. But when I turn the hw slider to off it turns the ch off too?? Despite leaving that...