Goto go and look at a boiler sometime this week,only managed a 5 min check on it today cust complaining of hot water not lasting very long,flow switch,diverter valve seemed to work ok with thermostat set to max water wasn't that hot,a reducement of inlet pressure made it hotter but reduced flow rate,the timer on boiler was not working at all,if the timer they are using now is only switching on ch could it be a problem that the heatstore is not being heated up?Was on my way out of door after fitting a new oil pump and they suddenly remembered this fault,so didnt have time to investigate properly with regards to programmer being used,so thinking maybe programmer or heat exchanger? any ideas??