No, people really are getting richer. Apart from people who are actually homeless (and probably also pensioners, who presumably aren't committing much in the way of gang-related crime) even the poorest people, i.e. those on benefits and in min-wage jobs, are better off now than they were 10 years ago. There actually is a minimum wage now, for one thing.
An important factor here is that rich people are getting richer faster than the poor people are, and the really crucial result of this is the stupendous inflation of the housing market, which tends to have the effect of polarizing towns and cities into 'good' and 'bad' neighbourhoods.
Nomad, you might like to know that class in Britain is much less rigidly tied to how much money have than it is (or seems to me to be) in America.