> I'm also wondering what the implications of this are for brexit

We're well into "who knows?" territory, but what would definitely happen is the UK would lose any say over the EU rules. The UK isn't really large enough to be its own market for startups (unlike the EU and US), so we'd mostly end up using companies hosted in one or the other and obliged to follow their rules.

(Safe Harbour is probably a more interesting one to consider!)