There may well be an issue with trying to charge using UK AC mains, as it's very different to the North American system. Here, our 230 VAC supply has a neutral that's at "earth" potential, and a line conductor that's 230 VAC above neutral. In North America, they use a split phase system, so that 220 VAC is has two line conductors, each of which is 110 VAC either side of "earth". As a consequence of this, I believe that the earth leakage check system is very different, and the charger may well not expect to see one live terminal at "earth" potential and the other 230 VAC above it, it will expect both live terminals to be at 110 VAC above earth, but 180 deg out of phase.
Best check with Tesla, as I think the onboard charger modules may need to be changed, or modified, in order to allow them to work on UK supplies. Might be an idea to see if there are any US service people that have brought Tesla's to Europe or the UK, and what, if any, modifications they needed to do. There's a fair chance that someone around one of the big bases has done this already, as I believe US service people can have their cars shipped here for free when they get posted.