Reasons for social segregation:
Housing - developers, buidlers and planners tend to build housing on blocks of land with a particular market in mind
Changing environments - houses built for large families in the Georgian times are now too big for an average family and have been converted into houses of multiple occupation by those on low incomes or students
Ethnic dimensions - ethnic groups originally come to the country as immigrants. As they are unemployed they are only able afford cheap housing. Therefore, newly arrived migrants concentrated in low income areas in cities.