I think more British people are beginning to think that the core concept of multiculturalism - the idea of each immigrant community retaining a degree of cultural separation - has severe disadvantages over the American "melting pot" model (not that racial tensions are unknown there of course).
While the commemoration of people's ancestral cultures is important, and brings great vigour and colour to life in Britain, it's as important that those seeking to live permanently in this country should respect and attempt to align themselves with the values, and to a certain extent customs, of British society.
Many people who are not dyed-in-the-wool racists resent the creation of ghettoes where some sections of the immigrant refuse to interact with the white population at all, don't speak English, don't respect democracy or the police, and don't function as part of British society in any meaningful way.
In my lifetime, the focus of racial tension has shifted from involving mainly the Afro-Caribbean population to mainly the Muslim population (which, thanks to ignorance, may also manifest itself towards other South Asian populations). When I was a kid, black footballers regularly faced a hail of bananas and monkey chants. Now, white lads proudly wear the names of Thierry Henry, Ashley Cole or Rio Ferdinand on their replica shirts. Yet in the same time the Asian has gone from being seen as stereotypically the man who ran the corner shop or the takeaway, or the doctor or pharmacist - a useful part of society - to being seen, in some eyes, as a potential suicide bomber.
I think the reason is that the black population has become more integrated - through shared loves such as sport, pop music, and simply by speaking English - while the Muslims have become more separate. They have their own schools, speak their own languages, and many seem to genuinely hate the white British, thanks to events like the Iraq war. Look at Northern Ireland, where two communities live in separate areas and go to separate schools, and see the hate that can build up where there is even less difference.
Sadly, all that has driven some of those white people who just want life to be simple, like it always was, without the threat of violence or a feeling of being a stranger in your own land, into the arms of racists like the BNP. All the racists in this country - whether the Abu Hamzas or the Nick Griffins - preach separation. We need integration to weaken them: after all, someone who's half white, a quarter black and a quarter Asian probably isn't going to hate many people on racial grounds!