Even though left-hand-drive is the standard in Continental Europe, we get very few here (other than tourists). It tends to be only a handful of US and European cars of a certain age which were never made in right-hand-drive. Believe it or not, 2016 was the first generation Mustang available as right-hand-drive from the factory, although small companies in the UK used to convert them. In the UK there's a market for used cars imported from Japan (Nissan Skylines etc.), but Japan is also a right-hand-drive market.
The main problem with vintage American cars in the UK and Ireland (other than their size and fuel consumption) is the lack or orange turn signals. There are some clever conversion kits which preserve the original look of the car, while other owners just wire in temporary lights to pass their annual test. I spoke to a General Lee replica owner at a US car show a couple of months ago, and when he took his car to be tested, the tester told him he couldn't test it because it didn't have headlights!