The answer is yes, depending on how old you are. For those still at school it might not be easy, but for anyone over 18 then yes it is. The only problem at adult education is proving that you have the level of knowledge to do the A levels. I've been in GCSE classes with people doing university degrees, or having firm college offers awaiting that C grade for English or Maths.
At the college I went to one had to do an assessment for English and maths to find out what level you were at to get into either class, but this may change depending on the college. I suggest you find your local place and have a word with them there.
As for online A levels, there are websites that do do online learning, but I have yet to find their Ofsted reports, so I'm a bit dubious in spending the cash to do such a course.
If you want to do a degree, without having the qualifications, then have a look at the Open University website. It is distance learning in the most part, with some onsite learning for certain courses. For the degree I would like to do it is £18K instead of the usual £27K. You can do the degree either full time, or part time etc. They also do financial help etc. It means you can work as well as study, so ideal for folks who can't afford the normal university route.
Never say never, just find the right pathway that suits you, most of all DON'T GIVE UP ON IT.