Nice work Gaz, would have been a few bob to get someone in. I had 3 heating engineers look at my Baxi it was only 5 years old but was working intermittently , one didn’t want to do it, one didn’t know what was wrong and the last wanted to replace the pcb.
i had a little look about and found the fan pressure switch was so high res it was taking 240 in and about 160 out, got the part and swapped it (£20) and was perfect after.
I wonder how they make their money?