A point not yet made is that Britain has a long history of immigration - forced and voluntary, going back 2000 years. Romans, Angles, Jutes, Saxons, Danes, Norwegians, Normans, Middle European Jews, Hugenots and more recently West Indians, Ugandan and SE Asians. As a seafaring nation there has been a steady trickle of immigrants into Britain for as long as we have been trading around the world. History demonstrates that these immigrants did integrate eventually (not always without pain and conflict) and most white British have a diverse ancestory which can be demonstrated by DNA analysis. We should be proud of our heritage and the contribution of "foreigners" to the British culture. We should be proud that people want to live here and be part of and contribute to that culture. It takes time for immigrants to integrate but it's happening to people of Asian & West Indian descent. I live in West Yorkshire. There has been a noticable increase in Asian integration over the last 25 years or so as they become more prosperous & move out of the "ghettos". Young Asians are adopting Western cultural norms and aspirations. There's still friction - but the situation is evolving.
As for Britain being the most hated nation. The Empire was imperialistic expansion, often violent and cruel. However, membership of The Commonwealth is voluntary with 370 million people (largely) happy to have the Queen as head of state and proud of their historic relationship with Britain.
What's objectionable is the racial hypocracy that is endemic in Britain and has been commented on above. An example:- Until recently our cleaners at work were two Italian women, both in their late fifties who married Englishmen and have lived in England for over 30 years. Despite this, they have both retained strong Italian accents. A gang of youths started hanging around outside the building and decided it would be fun to abuse them with threats of violence and obscenities as the ladies left in the evening. We notified the police, whose response was illuminating. "We can't do anything if no-one has been hurt". However when we said that there had also been some racial abuse (they'd been called "wops, eyeties" etc) the police came round like a shot, wanting witness statements, CCTV footage etc. What really stuck in the craw however, was the fact that the police completely lost interest again when they discovered the women were white!! This sort of approach does almost as much damage to racial integration as the BNP, who must be rubbing their filthy hands with glee at the propoganda potential.
As a side note - I'm white and have been subjected to verbal racial abuse in Britain and when I worked in India. There are half-wits of all skin tones, but most people are decent imho.