Whilst there are some very good home mechanics
Well you know what they say, when buying a car privately make sure you have a look at the owner's workshop. That will speak volumes as to how well the car has been maintained

I completely understand that some people prefer to have other people look after their car for them, there are all sorts of good reasons why this makes sense (lack of space or facilities, inexperience, no time, etc) but I do worry that people might buy a car believing that the presence of dealer stamps alone means that the car has been well looked after: whereas all too often it simply means the car has had the bare minimum of attention.
Your experience with your wheels being a perfect example. One job in the annual service is to remove all road wheels to inspect the tyres and re-grease the splines. Clearly in your case this hadn't been done - so what other service steps had also been skipped? The issue with rusting spark plugs in Ford engines is extremely well-known in the Morgan world, hence the numerous top cover projects we've seen over the years, and so there's absolutely no excuse for a main dealer to miss this either.