“could I not just take it around to my local Part M place and say "here build this" and it would be built to a good standard?”
You do not have to build it yourself, you can buy second-hand. LAA inspectors maintain the standards of LAA aircraft. The inspector has to sign off all the build stages and he would know if you have it done for you. You do not have to build it all, the rules say 51%. I took 1800 hours over 3 years 3 months, and managed to have a life at the same time. I did this by building it in my garage and getting the family involved. Some of the modern kits (including the “advanced airframe” MCR) can be built in 600 hours ish, but you do not learn as much. Part of the reason I built the more basic kit was to increase my understanding of the machine, as well as saving 4k.
If you want a way round the rules, get the aircraft built in the USA, with all the required LAA mods built in, and import it. I think the chances of getting away with this would be very good provided you chose a common machine like an RV.
IO unfortunately knows almost nothing about any of this and just makes it all up as he goes along. The completion rate of modern kits is very high indeed. 30 years ago, building from plans was almost the only option and that can take 10,000 hours, so the completion rate was poor, with many projects getting finished buy the third owner. Today, the LAA fleet (flying and under construction) is running at just over 4000 aircraft and rising. There are about 7500 sep C of A aircraft in the UK.
Rod1