European and Islamic cultures are starkly different. Why should Britain's Islamic communities be expected to integrate and let their identity become diluted? Likewise the British? Haven't we had enough enriching and improving? We are having enough trouble with the Americanisation/globalisation of our respective cultures without having to worry about fitting in with our new neighbours.
Of course orthodox nationalism has lost the day - we cannot talk of the nation state in a practical sense. Many, many races, ethnicities and cultures are here in Britain to stay. But we can look to the National Anarchist case: local and regional autonomous communities linked in federation. Communities and networks that can do their own thing - without having to 'fit in'.