"Integration is a problem in some areas, no idea what the solution is"
Marrying out of an ethnic enclave imo is the best way of integration, and that does happen with many 2nd and 3rd generations amongst some incomers, my grandfather was one such person who came to this country and married my English grandmother. No internet then so breaking the ties with the old country was far more absolute. Of course religion does bind some to their particular faith and that often precludes marrying out. When I grew up, being educated at catholic schools we inevitably had many Irish but Italians as well, and kind of old school ones that came from southern Italy and Sicily so steeped in some of their old traditions. For example, went into all black mourning garb when someone in the extended family died. Sometimes the older women in particular didn't learn the language, which kept them isolated. However, from what I gather the next generation, my peer group, threw off those shackles and just became English, so the only vestiges left were their Italian names, Italian food and hopefully they kept their wonderful language going. The contrary factor with some of those from the Indian sub continent from what I've read, is that the elders who came here in the '70s were possibly more assimilated as far as dress and customs, most notably the older women didn't wear the burka, or even the veil, but it's their younger generation who have embraced a hard line in the way they have turned to a more extreme version of their religion, and they would more likely to have been born and raised in this country which is puzzling.
Having said that, of course there are Britons who rock up in Spain and then make no attempt to learn the language or ingratiate themselves into their local community. Apologies for a bit of digression but talking of Spain, why do they put up with all these foreign gangsters? some are British and Irish who blight certain areas of their country, there was a recent gang shoot out around Marbella just wondering why some places are such meccas for crime? Why would any country want to import foreign criminal gangs?