Authoritarianism is a sliding scale. From what I can gather, lots of humans that have any political pull at all tend to be authoritarian (against the kinds of people they don't like, of course).
Not sure why you think the UK is an authoritarian regime. Check any ranking and it is one of the freest countries out there (Heritage Ranking, for example: https://www.heritage.org/index/ranking)
It's a fairly small network for an authoritarian government.
[0]https://www.cctv.co.uk/how-many-cctv-cameras-are-there-in-lo....
In fact, given how small London is that's a huge network.
London's population: 8.982 million
Area: 8,382 km2.
How is that small?
I see you're referring to the "Metro area of London". when referring to that size. The size of London proper is 1,572 km2 (Wikipedia, as well)
So now, the fun question is "what area is the camera count referring to?"
Further, the quantity of cameras matters less than the areas the cameras can see that is covered.
Even further-further is how easy it is for the government to acquire the footage off those cameras.
I think it's probably more like a survivorship bias than an innate quality. The only people who are capable of surviving in politics long enough to the point where they have any meaningful influence are the ones who know how to use the systems under their control to protect themselves while tearing down their opponents. Usually this means attempting to consolidate power in themselves, ie. authoritarianism.
edit: or making laws that are more about making it illegal to do something some people find icky or culturally unusual.
The word authoritarianism appears to have lost all meaning in internet circles. What authoritarianism actually is, is a people being governed without their consent by a government they did not elect. If British citizens, or their representatives decide they put significant value on public safety rather than privacy that's a choice.