I find it interesting how I got down voted for pointing out the same thing as you basically (just you did it with regards to China's report your neighbor program, while I pointed towards East Germany's report your neighbor and family program).
Now I totally get why I was down voted because obviously what East Germany and by extension the Russians did there was obviously bad and the UK has legitimate reasons and no ill intentions. After all its terrorism, right?
But look at it from a different perspective and it quickly becomes quite different. The East German state actors would have seen themselves exactly as the UK does now, completely in the right because they definitely are trying to find terrorists that are trying to undermine the East German state.
From there on it's a slippery slope and no doubts that the two are quite different cases in the end. But there's way too many parallels and if you want to tell me that there's not way too much potential for abuse, be my guest.
In case it was for lack of references here you go everyone: https://en.m.wikipedia.org/wiki/Stasi
Unlike China where this is current we have access to the "internals" with the Stasi and Germans can request their "Stasi Akte" (their Stasi case file to see what info the state had on them back when).
If you're into theatrical documentary style instead try to find a copy of "The Lives of Others" to watch: https://en.m.wikipedia.org/wiki/The_Lives_of_Others