I've got a Potterton Performa 28 which kept failing to operate giving me the fan/flue neon error - ChrisR correctly diagnosed a PCB fault. I'm with BG homecare - the engineer who came tried a new aps but after several other checks concurred with what Chris had said and ordered a new PCB. It was fitted the next day and has the boiler has been fine ever since.
It can be difficult on this forum to diagnose problems with some of the things we diyers describe but the experts are dealing with these things on a daily basis and have lots of experience. I respect their judgement.
I really do appreciate all the help that everyone including ChrisR have given us. There are some truly nice people on here.
Repair man is coming round' with the thermistor so lets see how he goes when i tell him i think its the PCB Will let you know how i get on.