People do a shit ton just to stay in college. I didn't realize this until I actually got to college. Some people work abnormal hours in a week and still take challenging classes and do well. Makes me feel like shit when I get frustrated after a few tries on a problem in class.
I don't know if England has the concept of community colleges. In the States, there is a social stigma attached to them, but if you're doing it to simply boost your credentials, a community college degree in psychology is not a bad idea.
Have you thought about simply buying a text book and just reading it whenever you get the free time? Whatever you want to know more about, something a teacher would be able to expand upon if you were in a class, you just search on the internet and probably will end up learning more about.
That's another route to go.
Nope, there are free and low cost college courses available to people between like 16-19, but thats the most you're gonna get. Our school system is completely different here.