It's entirely possible, I'm also 17 and took my first Psychology module in may.
But now my circumstance has changed and I'm about to start college again in a few days to start my A levels, with your situation though I think it's just a matter of motivation, if you're reasonably intelligent and have fairly good organisation skills you can do it, I think it'd simply be a matter of not letting the workload get on top of you.
Now as for funding, that may be a problem. I had managed to get my courses paid for in relation to my circumstance at the time, though I'm not sure how that would work with you, the modules can be quite costly depending on the chosen degree, though if you're accepted you will be given a grant at the beginning to help with start up costs.
Anyway, simply contact the main office about it, the inital process is rather lengthy though as you are under 18, Good luck