I am presuming that the +1 hour simply switches everything on as AUTO would but perhaps I am wrong.You seem to be fixated with your controller.
You also switch your controller OFF and then instead of back to auto you decide to create a different situation by using the boost + 1 hour instead. To diagnose faults you have to be consistent in your tests and not introduce new senarios
I am still not convinced of any fault apart from the boiler failing after about 20 min, but earlier you seemed to think it would run normally for hours on end if you selected a particular setting on the programmer
It appears to be kicked back into life when auto is Off then On again after 20 mins.
I am not fixated by the controller as I generally have faith in electronics and I do believe that something is wrong with the boiler it's just that the other day the water wouldn't switch off and that is why I reset the thing so I could reset the times on and off - that's all but now it only fires the boiler up when the HW is engaged (as well as the CH) but HW runs solo and the boiler still plays up.
Looking at the fitting and settup manual I see that HW can only be on either SOLO or when CH is called for on my system as it has two valves and one is controlled by the tank thermostat (HW) and the other (CH) by the controller (CH off).
As I said I will go through all your advice tomorrow (better than watching TV) and report back.
Thanks for all your help on Christmas day - it has been interesting learning much more about my heating system..... I really do appreciate your efforts.
If I ignore your own thoughts, are you able to view the pilot flame when it starts up normally and also when its in the fault condition?
Pilot light up Ok and I can view it through the little window. When boiler burner fires up green indicator comes on. When main burner goes out and the fan is still running the pilot is still alight - I don't think it the fan and pilot should be operating if the boiler is shut down because of room stat or water temp.
I will test to see if it plays up on HW only as well.
Regards
Steve