I've heard of this, too. Quite frightening. But, you know, it's the same as looking at the far right activists and/or the far left activists here in the Baltic States - there's usually a charismatic leader (or a small group of them) and a whole bunch of not-so-bright dudes getting shi*faced, running around and shouting about stuff they don't really understand.
I mean, England is a part of the UK, which, in turn was, at its time, incorporating so many different cultures - how can you have (and want) a big, powerful nation without listening to other cultures?
Sure thing, we've got to be vigilante toward terrorism, but that's what the government already does - holding potential threats at bay, without causing racial/religion-based hate (well, for the most part, anyway :D ).
My point is - these kind of movements are just as violent as any would-be terrorist, except, these dudes are half-drunk for most of the time :D