I must admit that I do not have a lot of experience on UK motorways. I did Folkestone to Shrewsbury and back last year, but did not notice any special difference in the behavior of motorists compared to the dense busy motorways in Belgium and the Netherlands.

So that begs the question for me: why would it be so much more dangerous to allow learner drivers on motorways in the UK? It does not seem to pose any problems on the continent.