I do A-levels at my local college and I don't pay anything (and I am over 25). At my college full time study is free. However, it's best to check with the place you want to go to. If you study as a full time daytime student, it is likely that it will be free.
I do not recommend home learning. It is exceedingly difficult and very expensive. Not to mention all the hassle of sorting out your own exams and coursework. It can work for some people but you have to be very dedicated. A lot people who sign up for A-levels this way don't complete them.
Access courses are another option, but completely different to A-levels. Depends which way of working you prefer. But don't feel stupid because you are a bit older. I am 34 and a lot of the people in my lessons are 17-20, although there are a couple of older people too. You are there to learn, and chances are they won't know anyway unless you tell them.