My view is that people here are far too trusting of those in authority, and in particular counter-terrorist police and security services personnel. The attitude seems to be "if they think they need this then they know best". The collective psyche seems to take more comfort in the moral character of the people given the powers than in the safeguards against misuse.
On the positive side, almost noone I know thinks that it's appropriate that local councils or the Food Standards Agency have these powers. Those parts of government are largely viewed as "nannying busybodies" and the "nannying" bits of government are mostly distrusted - there does remain a British sense of freedom.
What's worrying though is that people don't seem to believe that minor agencies actually have been given these powers. When I've had conversations with people about this the reaction is "you're just exaggerating to make a point" or "they won't really do that, you're just concocting a far-fetched scenario that's technically legal but wouldn't happen in practice".