There's been some discussion recently about whether certain activities, eg watersports, can legally be shown on UK websites. IANAL, and neither is the reporter who wrote this, but as far as I know, the first half of this article from February this year accurately sets out the current position. (The compulsory registration scheme described in the second part of the article has been abandoned by the government, at least for the moment.)
www.theguardian.com/culture/2019/jan/31/pornography-of-adult-consensual-sex-no-longer...
Incidentally, this guy is *the* lawyer dealing with these issues: www.mylesjackman.com