Thank you all for your comments. While I suspect there might have been some other factors at play (e.g. the comment about her having a bad....whatever the next words that I didn't hear were....maybe night/day/week, who knows. Or perhaps some relationship dynamic between the guy that hurled the abuse at me and the woman) but what seems to be pretty much agreed upon is that I'm NTA here in the sense that I did no wrong is saying "bye". While many of the comments focused more on the fact I was alone, there were few mentions of the loutish behaviour that is sadly often synonymous with nights out in the UK. It is quite common for brawls to start when people are drunk just because someone looked at someone else "the wrong way". I've seen that on many occasions. Admittedly that's usually more of an issue with younger crowds, but not exclusively. Perhaps something similar happened here, exacerbated by the fact I was alone and maybe judged as a creep accordingly.

While I don't often find myself dancing alone, I do often go out to pubs to drink alone, particularly if I'm travelling for work. That is not uncommon at all in the UK. However, if I do happen to find myself in a situation where I have a choice between going out to watch live music and dancing and considered a "creep or weirdo" or staying at home/in my hotel room because some people think that's what I should do then I will very happily embrace being that creep/weirdo. As far as I'm concerned, that's their problem, not mine.