90% of the children at my dc's school are non white.
All the butchers on the high street are halal. All the grocery shops (apart from Tesco and Costco) are ethnic shops.
Am I suppose to worry about this?
"how to tackle segregation and the cultural alienation that is now being felt by many, many people"
None of my white friends are bothered by it, and we all live in areas where we are an ethnic minority.
I think the OP has an axe to grind. 
"and frankly talking about disgusting imported practices such as FGM, first cousin-marrying"
We don't need to lump those two in together do we? First cousin marriages are usually consensual, and don't always pose a problem - particularly if both individuals can access genetic counselling prior to pregnancy.
FGM is a problem and I hope the government does all it does to tackle it. I'd also like to see all other types of non-consensual body modification (including male circumcision) banned for children.