I got ACCD at AS first time round. Now I'm finishing off my Master's at Oxford and I'm due to start my PhD here in October.
I remember that feeling of being so disappointed, and even my final A-level results weren't stellar (ABB- though this was back in the day when we didn't have A*s) and thinking that even though I'd gotten into a decent university with a decent department, academia and studying clearly wasn't going to be a long term thing for me. How wrong I was!
In short, don't let your A-level results make you think that you're not good at studying or that you're not intelligent, because with hard work it is still possible to turn things around.