Recently had my boiler, a Baxi Solo HE serviced, as it kept cutting out, red lockout light on constantly. The boiler seemed to work ok for a period of time after that and then started doing it again. Last night even after pressing the reset button the boiler refused to start. SO in my infinite wisdom as a non expert I carefully took the front of the boiler off to expose the burner and electrodes. The first thing I noticed was a fair amount of oxidisatipon on the electrodes, so with some very fine emery cloth I cleaned them up AND did the same for similiar looking 'rod' next to them which I assume was part of the temp sensor? Put the whole thing back together, fired it up and great, all started up ok. Unfortunately after about 30 mins of use the boiler cuts out with red light flashing indicating an overheat fault, never had this before .... Have I done something wrong? if so what can I do to fix? - Thanks in advance.