The UK have been spying on everyone since the concept of a paper based records was conceived.
I even caught them in the 90's spying and interfering with computer systems without a warrant, which is why section 56.4 of the snoopers charter exists. Every state controlled database is used to monitor you, beit your school reports, nhs records, "anonymous" std clinic visits, tax records, telephone records, DVLA, GCHQ has to gain access to each and every computer system not only here in the UK but in the world. The spooks even try to hack your mind using psychological techniques & chemistry.
The first trick is to convince the population the UK military adheres to its own laws when you can never trust a country that operates in secret.
Put it like this, if you dont have the intelligence, how can you nip things in the bud before they get out of hand?
Now look at what countries suffer real acts of terrorism and which countries dont.
What countries like to suggest that members of the population, typically female, is spying on you.
Females are natural born liars as they dont have the physical capabilities like men to get them out of trouble. In the words of Rolf Harris, "can you guess what it is yet?".
GCHQ. Always listening to its customers!