Yeah, I've only heard of Cambridge asking for UMS points.
First, don't worry. If you did so well in your GCSEs you may have done just as well in your AS levels. I thought I had totally messed up a couple of papers last year and actually it turned out I had done really well.
Second, some schools do not certificate their AS-levels and so, I think, in these cases it's not compulsory to disclose your AS grades on your UCAS form. You really should check what your school's policy is on this. It is, I'm afraid, unlikely that a top 10 university would consider you with BBB(B) at AS. Even if your teachers predict AAA, they'd proabably still think you intended to resit, which I think is frowned upon. If, however, you have AAB you stand a much better chance but you really have to convince them you'd be capable of getting AAA. Law's getting more and more competitive and you have to realise that the competition is very strong.
Good luck with your second year and don't worry too much about 18 August.