I'm not sure that anyone on this side of the pond has much of a clue - least of all our politicians
If you are buying new from dealers, then at least any UK VAT will be removed from the sale price (or should be!) because UK VAT shouldn't be due on exports. So you would pay any import duties & VAT charged by your own customs on import, but wouldn't pay the UK VAT. At least, that is how it should work.
If you are buying used (for example, private sales on Ebay), then there would typically be no VAT, but your customs may well charge both duty and VAT on the declared value.