Oops, posted too soon.
You cannot draw parallels with London, which if anything is a victim of its own success. As I said, middle-class people (often white, often young, professional and childless) are moving into previously "ethnic" areas of East London, other middle-class people (often white, usually having families) are moving to the 'burbs for bigger houses, recent immigrants (often white too!!) are arriving in the poorest areas to sleep 6 to a room, second-generation immigrants are moving to bigger houses in nicer areas as their prosperity increases......
All thriving cities are in a constant state of flux, and that is what makes them great.