I think the argument is less that inequality has increased overall, and more that the country is increasingly stratified by geography - with greater concentrations of wealth in the South East relative to the rest of the country.

This is especially true in formerly undesirable areas of London (e.g. Hackney, #10 on the 2003 list) and towns within commuting distance of London (e.g. Hythe, #3).

Presumably this is due to the gradual shift to a London-centric services economy as well as the increasingly ludicrous price of houses in Central London.