MY girlfriends Apollo Fanfare 30/50 (I think) si lights when the heating is first switched on, runs for 30-40 mins then shuts down. You can hear the igniter clicking but the boiler fails to re-light. Once it has been left for a while and the timer reset the boiler will relight and run again for 30-40 mins. The igniter has been replaced as it was 'burnt away', but this has made no difference to the fault. I don't have a manual..is there a flow or temprature sensor issue. If so which is which...can I test?