As thrilling as the debate is :roll: one thing matters more in the story than anything else. A fellow engineer saw the flue with his own eyes and decided that without intervention the installation could become dangerous.
If anyone reading this thread made the same judgement then I doubt...
The flue screws are to stop the flue coming apart when you pack away the Xmas decorations and chuck them into the loft. You can trust this guy (unless he only went up there to wee in your water tank )
The leak is the main problem I should imagine. Get an engineer in to fix that and tell him to bring some fast blow fuses for the no power issue and then get him to tell you off for removing the cover of your boiler !
I'd be thinking that it's the pilot burner. Probably a 25 minute job and quite a cheap part - could most likely be cleaned up. Is the boiler still sparking after the pilot is lit?