Well it is certainly possible to get accepted on courses on higher grades than your AS results, but only if your teachers will put you down as predicted higher grades, but they're only going to do that if you actually have a chance of getting then. I had a nightmare in my AS results, with ABCDE, and ended up with AAB, but I wouldn't have even got the offers for AAB if I hadn't been predicted them.
On the other side of that, I have a friend who had poor AS results, and do was predicted BBC, so has gone to Leeds Met, but ended up getting ABB, but because the teachers wouldn't predict her higher grades, so she ended up going to Leeds Met.
I would agree with Pandy, the best thing is to convince your teachers to give you the highest predicted grades you think you can realistically achieve, then work as hard as you can to get them, and hopefully you will end up where you want to go, thats what I did, and it worked for me.