Like it or not these things are done at the will of the people of the country; they could vote to change it, or vote in people who would change it but they won't. It's horrible and unacceptable to you, and to me, but not to your (technically, our, but I can't vote in the UK due to residency requirements) fellow countrymen.

Humans fear devastating but statistically unlikely things disproportionately to their chance of happening, and will do basically anything to avoid them. Terrorism is such an example, and surveillance is a consequence.

Thing is, if the people of the UK decide it's an unacceptable tradeoff they will vote to change it, and it will change. Just look at, lord have mercy, Brexit. It's in everyone's hands. That's not true of a billionaire's discretionary fund.