Check that the pin on top of the diverted valve is hitting the switch properly and that the switch is making. If the pin isn't moving far enough and you have had the diaphragm replaced there's a filter on the cold inlet that might be blocked. How's the hot water flow at taps?
Pin is hitting the switches and boiler fires (cir-clip not refitted fully previously). As I have read previously, heating was on last night and hot water the produced at taps. Water at taps is running as it always has just barely warm. Not sure we to go next?