1. I would say yes, you hear it and the engineer took it out to witness it sparking.
2.Yes
3. Yes in most cases during the cycle, however it does go off immediately when it fails and starts the process again until it lights and (majority of time) stays on or it error codes
4. answer in 3. Yes but the issue of non starting is intermittent but on a daily basis at some time.
5. Yes
6. I cant be sure of the difference
7. Yes
Adding to this when it runs which it also does every day, it seems to run well, water and heating as expected, until the intermittent recalling for either heat or water when the temp drops, then is when the start process can be intermittent.
Hate boilers but we need them. I may well have to bite the bullet and instead of getting the engineer again, call and pay ideal the fixed fee, which i suspect will not be that cheap, I suspect it may be something on the electronic or electric side, maybe the ignition module or a lead rather than the actual igniter, which seems to run worse that the older one removed.