Hi, I'm in Year 12 taking Psychology, Sociology and Biology.
I'm exactly the same as you - I want to be a forensic/criminal psychologist. I have no idea why I'm doing biology, I hate science HOWEVER the A-Level content for psychology does include quite a bit of biology, so in theory it does help.
Sociology links in quite well too, just to echo what the other person said!
Feel free to ask me any questions, I'm also intrigued by what other people say on this thread.
:-)