Social mobility - or masters without slaves?

We seem to be hearing a great deal about social mobility, or rather the lack of it, these days. The New Labour elite are a bit unsure about the whole concept and claim  to be in favour of old fashioned class pride and solidarity. Bit late for that you might think. Little Clegg thinks that it's a jolly splendid idea and that we could all do with a lot more of it. I imagine that David Cameron thinks that social mobility is a bit like time travel and just about as realistic. Meanwhile the Pol Pot school of thought on the subject is gaining ground in some quarters. Spiked's Brendan O' Neill thoughts are worth a look but as my own  small contribution to the debate can I just ask why it is that in post-Blair Britain an aspirational working class person is always assumed to be incapable of aspiring to anything beyond lining their own pockets?