Very early days for me as I only ordered a M3LR a few days ago. Tesla offered £2000 for my 2009 Volvo V70.
Not a lot and I guess it complicates the delivery/collection process with the trade-in as well.
My suggested availability is in June.
If you are prepared to be flexible, then my experience is that the SC may be accommodating. If you have a custom order that doesn't happen to match something already in the UK, then I would realistically expect Q4 2020 earliest given that Fremont is currently making ventilators & when back up and running, US orders especially Model Ys will take priority.
I had ordered a Blue LR/19" sport wheels back in February just before a couple of months visiting family in the USA. i was fully expecting this to be available May-June-July....whenever & had sold my previous car so was going to borrow family/friends cars when necessary once we returned end April.
We came back early when the UK Gov't asked all UK nationals to return & on arriving home found that my wife had been re-registered at our local hospital as a key worker (we retired early a couple of years ago).
I called Tesla because nobody was then going to loan her their car for obvious reasons, said I was prepared to be flexible with colour (Blue, White or even Red) and wheels as long as we had a LR or pay slightly more for a white M3P (I'd been registered for -£3,500 on the OLEV portal just before midnight on 11th April which applied to any model). We were in self-isolation for 14 days so she needed the car at the end of that time.
Within a day they had called back found a white LR with 19" sport wheels which was delivered 2 days later, easily in time for her return to work.
(....as it happened, before we went to the USA my Daughter & I had called into the SC and she immediately fell in love with the pearl white colour & said the blue looked very dark and less appealing - I tended to agree & slightly regretted not changing the colour to white at that time).
So flexibility in giving the SC several options meant that a match was easier and faster & in the end I couldn't be happier (apart from me rarely using the car & being very careful too wipe & clean every surface when I do)