My impression is that the segregation in the North is based on a few things from which lessons can be learned, although not necessarily easy ones. The first one is that although the kids do go to the same schools, a lot of the housing is racially segregated in a way that doesn't happen in London.
The other is that the British Asian identity has become a lot more religious since the late 1990s and I'm not completely sure why that is although things like the Gulf War and Islamophobia haven't helped. Or certain sections of the left pandering to religious "community leaders" rather than engaging directly with communities.
There ARE common cultural activities that the kids are into, especially football.
to me, it as at least as much a politics of class as it is a politics of race. as in, all the problems that might be ascribed to race are really about poverty.
I think you are talking years, generations of institutionalised poverty, poverty as a way of life, that cannot be compared to the same sort of poverty in London. I think cos the cities around that poverty (eg, let's say, Bradford) are really struggling, in a way that London is not. Also maybe the cheek by jowl nature of London, whereby you might have one rough street, one millionaires Street, next to one another, whereas up north, poor areas are often hidden away in their own little maze of cul de sacs and crescents, dead ends a long way off the main road.
i think the sense of isolation in some northern areas is really pronounced, compared to london. like public services for eg, municipal lesiure centres and the like, or public transport. london is so good for that, whereas some places up here, getting a bus to work can be a major issue.
Islamophobia is now at least 20 years embedded as well so this is a factor, especially cos up north, certain areas are not actually that multicultural, especially some of the very poor areas, they are like 50:50 white/asian. it becomes quite binary.
football... well, i do think it breaks down barriers but something happens i think, between primary/junior and secondary, where splits happen. and i think i would broadly agree with blockhead - it's not enough really. plus there's less footie embedded as a leisure activity, less places to play it. but sport is good at breaking down barriers as well, no doubt.
there has also been years of new labour social exclusion mess up here, same as everywhere else, blue sky thinkers drafted in to 'sort' community cohesion by forcing people to meet one another in false ways that people see through. very shallow, possibly well meaning but ultimately not real.