what boiler have you got? , some boilers have a pump overun, which means the pump will run after the boiler has shut down to disperse heat from the heat exchanger
was wondering if anyone has the fitted the new baxi roomsealed backboiler ,it has a 10mm condense that you can clip to the skirting, that would look good lol
sounds to me like the plate heat ex needs taking out and cleaning, if it was the diverter playing up it would throw the heat down the flow into the rads ,