MCR01’s are used for training, just not in the UK.
And X'Airs, Vans....
... The UK has it's own approach to airworthiness, which is fairly rigorous, but occasionally hard work.
Which controls privileges based upon a mixture of initial airworthiness, maintenance, and ownership. It is not an identical system to much of the rest of the world.
It works, and there's of course never anything to stop any aircraft owner exceeding legal minimum requirements - and most do. It often gets called "fettling" !
G