Economically it's gone downhill, more obviously in recent years, but it's been declining ever since Britain stopped being a world power. Socially/culturally your opinion on whether things have gone downhill will depend on how good you think the culture was in the past. Britain has much less time for "traditional English morality" although some residue from it does remain. I don't view immigration as the primary reason for cultural change. It has certainly created a very diluted and chaotic culture, but I think shame over England's past is the real reason culture has changed so quickly. After all, the Muslims have no problem keeping their culture alive even as a minority.