Muslim immigration...
Maybe it's a part of the explication, but only a part. Because there's a lot of causes to emigration. For instance, actually in France, there's a lot of emigration to Belgium in the higher-class because taxes are lower in Belgium. And there's a lot of emigration from Netherlands or UK to France because houses are far cheaper...
And you'd be right, same is happening here in the UK. I hate to say it but it's gonna be high noon for Europe if someone doesn't stop these muslims. The fact that the goverment can just sit there and do nothing is one of the most shameful episodes in UK history!!