I've not seen out and out snobbery at all in London universities, although I once was abused and nearly attacked by a drunken idiot on a London night bus for having a Northern accent (apparently he said that Northerners were all inferior to Londoners and thus should all ******* off home!).
However, I think the real point is whether working class students are still able to study at London universities, or whether financial reality or Government policy has forced them out. I would say that the top 20 unis have always been middle-class bastions due to their reputation and the high A-Level scores required, and this ultimately causes problems for people from working class backgrounds getting into areas such as finance, IB, Magic Circle Law etc.