Re: FFS
If those companies are in the EU27, Britain must trade with them in line with any agreed trading rules with Europe. That's kind of the whole point, whether it's done under a deal, or onerous WTO rules. Brexiters like to say that Europe trades more to Britain than vice versa - and that;s true, as a net sum, which hides the reality that a far smaller percentage of EU exports go to the UK than vice versa, and this is why the EU27 were in a far stronger negotiating position. Only 2 EU nations are exposed badly, and can be supported by the bloc, while the UK would taker a serious haircut, potentially exacerbating the rate of companies exiting too.
WTO rules would also punish companies using the UK as part of "long workbench" cross-EU manufacturing - like the auto industry. Expect the golden handshake deals given to keep the Japanese car companies settled in the early days of Brexit to get picked apart quick enough if there's no deal.