I would agree with your posts so far, except for one detail - the far right HAS had power in this country to the same extent that the Republicans have in the States - under Margaret Thatcher. It wasn't left-wing protests or a recovering economy that caused the National Front (the fomrer BNP, to all intents and purposes)to wane in popularity - it was Margaret Thatcher's pre-electin speech about britain being swarmed with immigrants. Hey presto, all but the most extreme of right-wingers suddenly started voting Conservative, and we had a government in power for thirteen years that was only three steps to the left of the BNP, if that.
I also suspewct that the same thing will happen again with Cameron. He may be presenting himself a sa reasonable, moderate new school Tory, but once the Tories get into power you can bet your boots they'll start showing their true colous again.