The people who know anything about spies are not going to reply to a thread such as this.
I was nearly involved with SIS in some capacity and the amount of background probing was enough to make me scared for ever being closer than I have to be.
I can say with confidence that if you've been in the apparatus then you wouldn't even want to say anything. There's a lot of brainwashing that happens too (you could see the outcome of the Snowden revelations for example) so people would be very defensive of the concept of giving out info they have and extremely likely to be motivated in hunting down "leakers".
I was nearly involved with SIS in some capacity and the amount of background probing was enough to make me scared for ever being closer than I have to be.
I can say with confidence that if you've been in the apparatus then you wouldn't even want to say anything. There's a lot of brainwashing that happens too (you could see the outcome of the Snowden revelations for example) so people would be very defensive of the concept of giving out info they have and extremely likely to be motivated in hunting down "leakers".