I think what we need to appreciate here, is that attitudes are vastly different between the young and the elderly.
Older people remember a different version of England...where overwhelmingly the population was white (affording them the opportunies to put up 'No dogs, no Irish, no black' signs and spend delightful weekend '***-bashing - I know of this, because a group of NF supporters managed to put a school friend from India (yeah - I know...ironic isn't it).
However, younger people have no recollection of Britain in the 50s. They have black, Turkish, Muslim, Hindu friends.
They eat kebabs, jerk chicken,feta cheese, calzone, beef madras and listen to Wiley, Dizzee, Roll Deep, N-Dubz etc.
I'm in my mid-forties, and cannot remember a time before London was a very multicultural city.
The answer unfortunately is to wait until certain people, well...there's no other way to put this: die off. Think about it - in 50 years time, who's going to be around to remember an all-white Britain? People's view of urban normalcy will change, because that's all they would have ever known.
...apart of course, the producers of 'Midsomer Murders'.