Agree with Cory and disagree with all the posters advising random vocational courses simply because they're vocational.
History opens doors to civil service, gov/local council jobs, media, publishing, museums, heritage etc. Not just teaching! Though of course that's an option. (I don't know any historians who've gone into social work, seems a rather odd vocation to link to a history degree, though obviously it's possible). None of these professions are massively well-paid, but you can still make a decent living.
Plenty go into law and earn good salaries via the conversion route. If your history degree's from a good uni a firm will sponsor you to do the conversion course and give you a training contract. Not sure how mature students fare in this context, but I imagine your life experience/mature gravitas would not be unhelpful in dealing with clients etc.
History's also great for transferable skills (writing/argumentation) and encourages you to think out of the box and consider problems from multiple angles (not just your personal opinion).
I do know one historian who went into financial/business consulting (problem solving skills) and makes an eye-watering amount, so that's possible too. Then, if you're really academic, there's academia (but that is a fairly badly paid/high pressure work environment with few jobs. But I do know a successful mature student turned academic with a FT position, so again possible but difficult).
Also note that Library/Archive studies itself is a degree option too (can be quite a hard course to get into I think -- only a few unis do it (one is UCL, maybe?) and you need prior experience. But I met a couple of people doing it and they seemed very happy with the course. There were a few mature students in their group too, if I remember rightly).
I'm sure universities have meets/socials for mature students. I've got to say, when I was an undergrad we didn't really socialise all that often with the mature students (we felt like kids, they felt like adults, so we kind of expected them to take the lead if they wanted to be friends (which, in hindsight, probably isolated them)). But often they had more rapport with staff, and as I say I'm sure there is a central hub for mature students at most universities.
Good luck OP. Enjoy it!