It happened in 2011 - you've got yourself a little bit 'the sky is falling' here. My boss (a brown lady) flew in from Turkey at weekend, back from a family holiday expecting a hail of bullets and a fiery wasteland. She was surprised to find the UK behaving pretty much as normal. The Daily Mail plays its part, but there's also been a consistent failure of the left to build a positive message about immigration and what it does for economic prosperity - and there has also been a failure at the social level by people of all skin colours to effectively integrate with each other outside of large metropolitian cities like London, Bristol and Manchester. These things all need addressing.
But make no mistake these are racist idiots, albeit slightly more organised than the usual racist idiots - but they don't represent the majority of British people, or indeed Britishness more generally - at least in this Penguin's mind. They will smash a few shops, get fired into prison and fume themselves to irrelevance. The counter-terrorism unit will use this as exactly the reason they needed to throw some of the violent instigators into prison.
They didn't manage it at Cable Street and that was when fascism was all the rage - they've got zero chance now. The sky isn't falling, it might be slightly greyer, but that's not something to worry about too much. :o)