The only way that 'undesirables' could be identified would be by increased checks in all walks of life, from travel to housing to employment to banking and so on.  It would be no good simply relying on border checks because not only are there many ways to avoid these but in practical terms thorough checks of every individual would make cross border travel impossible in the numbers we are used to.

The introduction of ID cards, DNA databases, email and telephone intercepts etc.  All proposals suggested that are the opposite to the British way. 

There is no way that life would be 'normal' as you suggest.  As the article I linked to earlier by Simon Jenkins describes far better than I can how such changes are handing the terrorists a victory.

"I measure my success in column inches and television hours, in ballooning security budgets, butchered liberties, amended laws and – my ultimate goal – Muslims persecuted and recruited to our cause. I deal not in actions but in reactions. I am a manipulator of politics. I work through the idiocies of my supposed enemies."