Happy Hacker - I would very much appreciate that checklist or guide you referred to written by a friend of yours. I will PM you.
Also meant to thank SPB for his input.
I think elements of the rules cause confusion because changes are not well explained. Metal CU's being one such example. The question comes up in forums sometimes as to whether a CU can be mounted on a wooden backer (say plywood cladding on a wall within a cupboard) or whether it must be mounted on intumescent material. I have not referred back to my recent 18th Ed copy but I think it is silent on the matter. You just need not to have potential causes of fire (like live bits poking out).
The Tesla example of earthing I gave above was when Tesla were ramping up their sales about 3 years ago. They provided a domestic charger unit with the car. This was confusing to a number of electricians as CPC arrangements were not super clear at first so an electrician had to look carefully. My friend the electrician went to far as to consult building control on our first one. There was no issue with TT rod at my rural house, but my partner lives in a built up street in London and goodness knows where metal gas and water pipes may be underground. The system was equally confusing to users, as the charge points arrived pre-set to the minimum charge rate (the "takes forever" setting). Anyway, I digress. Has proved to be a very helpful thread for me.