There are a good few US cars in my Town and there where two down my street for years,and out of the US cars over here and not heard of any which are hard to get over here.Also in my town is this event which takes part every year.
Americana International Show <Linked.
As for imports from any country here they still need work to be done to make them legal for the UK roads but not as bad as you guys get it in the US but bits do still need doing here and they have to pass test before they are allowed on the road.