Having pored over stats, the only undergraduate colleges where state school applicants were on average more succesful than independent school applicants in 2004 were Robinson, Jesus and Downing. Even at King's, state school applicants made up 79% of the applicants but only 72% of the offers. Of course, this puts a lot of stock in figures where we don't know about the average -quality- of applicants, but all things considered equal King's discriminates against state school applicants.
In 2005 the only colleges where the percentage of state school offers is higher than the percentage of state school applicants are Peterhouse, Magdalene and Trinity Hall. How interesting.
Basically, all this tells us is that it is really stupid to decide a college based on some perceived idea that it discriminates one way or the other. A college famous for discriminating "for" state schools actually goes the other way, as do two famous for discriminating "against" state schools.