I did an A level in Classical Civilisation a couple of years ago. I absolutely love the subject matter and just fancied having a go.
I did it via distance learning. The materials were very good and there was a tutor to mark essays but that is pretty much where their involvement stopped. There were message boards which were basically frequented by me and two other other mature learners, and it was a shame that there wasn't more engagement there, tbh.
Like any distance learning experience, it can be a bit lonely at times but I did really enjoy it.
My advice: there are absolutely tons of resources out there on the exam board websites, including marking schemes, examiners reports and past papers. There is so much more info at our fingertips than when I did A levels the first time round. A detailed syllabus for a start!
Then, a but of clever googling will bring you to school websites with revision notes, presentation slides and all sorts of other useful info.
Finally, I found the Student Room really helpful for its subject led message boards, tips on revising etc. It also has a sister site called 'Get Revising' (I think??) where you can created your own revision notes and flash cards etc, and browse what others have done for the same subject and examining board. I found that incredibly useful as it sent me off on trains of thought i hadn't considered before you can also use the site to create revision and study plans.
I did my exams at a local school via the adult education section of the local council. That was a little odd, sitting in a large hall with everyone else taking their Maths exam!
I did my A level through the National Extension College, and they also have regional exam centres around the country where you are guaranteed a place. I didn't need to use it because I could sit locally.
I'd love to keep learning and my dream is to take a Classics course at uni. Perhaps i will one day!