A-levels are a very long way away now, so I can't remember much about them. I didn't have any real problems with the PPL writtens - just read the books through a few times, tried to "understand" the why of each rule etc, then had a crack at some practice papers.
If it makes sense, and you can understand the thinking behind the various bits, it will become like a language you speak.
The only hard bit is the air law: for that, I took the textbook on a two-week holiday and sat under a palm tree while I pickled it all into my head (with liberal doses of the local hooch), then flew home and took the written the next day. Passed it, too!
I'd forgotten most of it within two weeks.