It's quite striking to read up on the differences in definitions of social classes between Europe and the US. In the US, class is almost entirely about income bracket, in Europe, class is mostly about your social network.
What's also interesting is that (as a culture) we don't stigmatize working class who've become rich, nor upper class who've become poor - but only efforts to cross the class boundary. Perjorative terms like "nouveau riche" and "mockney".
There is a world of difference between the social status of the grandchild of an aristo who gambled away the family fortune, and a chav single mother. The former has access to contacts, a peer group, a social network (call it what you will) and even people they deal with every day will treat them with more respect. This at least is nothing to do with actual spending power.
But our hypothetical ex-aristo would be rejected immediately if she tried to become working-class (tho' probably she could become a chav).
In my experience, class in the UK is primarily determined by who your parents were, not by who you know - with there being notable regional differences in the permeability of the class distinctions.
