Not unknown for UK owners of American metal to put the UK registration onto American style plates. If done at the back, certainly illegal, but the front is another matter as a smaller plate can be used on imported cars where there is not space to put a full UK plate.
I've not heard of anyone being done for this, it would not be an easy case in court and the offence has a relatively small fine and no points. I believe a cherished number plate could be taken back by DVLC but I've no knowledge of that actually occurring either.
