I have to tell you I am not that bothered.
Twice I nearly lost my father to terrorism in London. (Sliding Doors commuter moments both times — by sheer chance not being in the very usual place at the very usual time). I remain pretty relaxed about the idea that people who wish to bomb trains and tubes and buses can't get across London without the awareness that they could be tracked.
You cannot live your life paranoid, and while I think the evidence is clear that we need a small readjustment with the security state (as is evidenced by the BBC's extraordinary battle to get them to admit they lied to a court about a neonazi agent) I think it's better to understand that, yes, sometimes people are watching.
Better than the pretence that constitutional rights protect people they clearly do not protect, or that because the CIA or NSA promise not to do something, they aren't doing it.
I don't think there is any benefit in importing the paranoid style of US politics (R. Hofstadter) to the UK. And I think the weird breathless panic Americans have about London is their problem. We, living here, shouldn't choose to imagine it is true, when it isn't. London is safer than every comparable US city and transport policing is a big, big, big part of why. And if freedom-loving Americans have scared themselves too much to visit, I am not sure why we should care.