Just a FYI, I used Birmingham Digbeth which I understand may now be relocated.
My first MS P85D in September 2016 came with an original plate so I went through the malarkey of assigning my cherished plate to the 'new' car had plates made and tried fixing them myself - this I effed up!!! (Forgot to tell my insurers of plate change - but that's another matter) Phoned Tesla, they said bring it in and we'll fix it which they did but had to change the rear number plate mounting all free of charge. When I had the car MOT'd in November 2018 it was failed as two of the digits on the plate were 8mm too far apart. So had another set made, phoned Tesla and they fitted once again free of charge. I then purchased a new MS P100D in June of this year having sold my P85D privately to a dealer (R Symons - excellent in every way) and having changed the plate back to the original kept my cherished on 'retention' which I supplied to Tesla prior to purchase. Tesla did all the registration, supply of plates and fitting (just to be boring) free of charge.
I imagine that with the vast increase of the UK Tesla fleet as a result of the M3 arrival in the UK they are getting more requests than ever. What I will say is that, to date, my dealings with Tesla Birmingham (or at least Digbeth) on all matters has been exemplary. Maybe they are the exception. Maybe I've been lucky. Who knows.
My feelings are that Tesla will have access to exactly the right dimensional size plates together with the expertise - and if it goes pear shaped they will have to sort it out.