If there is no deal (refer above to NO WAY) then the UK is putting a 10% tariff on car imports so Tesla would save 10% on each car building them here. In right hand drive.
Would be great if it came to UK but I am sceptical in the short term.
The UK/EU already has a 10% tariff on imports from USA, so this is also the current position. Any future UK saving comes either from a zero tariff on imports from GigaBerlin, or a zero tariff from USA after transition.
A UK Giga Factory would cost whole wad of cash to build and run and eat into any 10% saving, so likely only becomes attractive is if there is a No Deal Brexit and the UK GigaFactory costs < shipping & Tariffs from elsewhere. But bare in mind that with a No Deal with EU would likely come a trade deal with the USA, so costs of US imports could get massively reduced making Fremont imports cheaper.
I guess the other variable is if he UK tax payer pays Tesla sufficiently to make the venture worthwhile
Whilst the UK is an important and big market fro Tesla, a GigaFacory in the UK on the scale of GigaBerlin would likely be far too big, unless the UK would also export... which then begs the question to where? Under a No Deal the EU would clearly not be attractive for exports, with a zero EU Tariff a UK Giga does not make much sense (can import from EU for free), and USA is out with their local production... so where? Right hand drive for the small Irish market might make sense.. other than that.. we are looking at long shipping times.. so why build in the UK?, a Giga elsewhere seems more logical first.
The other big issue is political stability in UK, whilst we are now out of EU and heading out of transition soon, it is not impossible that closer EU ties will be reestablished to some degree by future administrations making long term returns hard to predict without (expensive) government guarantees.