I actually thought you *were* an installer! Take that as a compliment, I think!
Lol, unfortunately not, in another lifetime maybe.
I was in the same boat as yourself a few years back and done many many many hours of research. There is a lot of misinformation around, and there is more than a few old dogs who refuse to change their ways and will always only for 1 brand of boiler regardless, and discount many new innovations, mostly because they just don't like change. A lot of it is they just want to fit something as quick as possible and get paid and move on. Taking there time making sure pipe routing is good, etc etc is unnecessary, they know that 99.9% of people don't have a clue and as long as they have heating and hot water with no leaks that will be the end of it. Most people just put up with minor flaws.
I liken it to car owners most don't even bother getting them serviced, slight noises get ignored, funny handling gets ignored only when something breaks or it stops working completely to people then take notice.
I like things to be right, especially if I'm paying for it, it does wind trades up, they prefer to work for people who are clueless, and I can see it a mile off in their body language and lack of communication after the visit.
Luckily there is trades out their that have the same principles as me, they are hard to find mind.