I've just ordered one. Will the existing standard UK plate fit ok?
Yes mate they do, the little red bits of rubber keep everything in place. Well worth buying genuine ones, as the others you can get are cheap and nasty, I got mine from the local main dealership for about £12...saved me waiting for delivery.
NB: The little black plastic circles above the H
break off, use them as your washes when you screw it to your car! I didn't notice them until after I'd turned the house upside down looking for a couple of metal washers to do the job!!!
When you take your plate off you will see some grey/black sponge, I kept that on to protect from any scratching and to stop and possible rattles!