Dialect Levelling

My understanding of English Language is that the dialect has levelled out as time has gone on. The main reasons for this are immigration, technology and education, the levelling is where the dialect become becomes homogonous. The main area this takes place in is London due to it being a capital city with the main airlines, factories and distribution centres being there it entices immigrants to visit there increasing the language diversity around London, it then gradually moves outwards from there.
Paul Kerswill argues that dialect levelling is taking place outwards from London rather than in London in four areas. Paul says that the centre of London is diverging from the rest of the country when it comes to dialect meaning that when it comes to the edges of London Estuary English is being spread further across the country. In the centre of London the language diverges from the edges of London whereas the rest of the country are converging with the edges of London, the reason for this is because of the vast number of different cultures around central London as well as the majority of the population there being working class meaning they do not have the money to move elsewhere.