I honestly don't care about that. They let these people in, and told them to have all the rights that are granted to Englishmen. Furthermore, they are constantly telling them how Islam is great while publicly flagellating themselves over their imperial past and their own church pews are empty aside from the old and dying. Is it any wonder they look around them, see a decadent society and want to remake it as they want it to be?
If you don't want that to happen, either you don't let immigrants in, or you let them in under the condition that they assimilate and become like the other citizens of the country and if they are not happy they can fuck right off. If you open the door, tell them they can live their lives as they wish as long as they obey the law, then things like this around bound to happen. And really, why shouldn't they?