1. This was certainly true of Guy Burgess, his sometime (iirc) lover Maclean, and Harold A. R. "Kim" Philby. I'm not sure about the fourth man in the ring, Anthony Blount. Someone may recall the fifth man in the group, who iirc was high up in British counterintelligence, MI-5.
2. These spies were recruited by an as-yet unidentified faculty member at Cambridge.
3. Other articles I've read have claimed that numbers of the "Oxbridge" university faculty were gay, such as Lord Keynes. Faculty would sometimes entertain students at evening soirees in their quarters, and these evolved into a social scene. Homosexuality was rampant -- the colleges back then were for men only -- and some of the social circles were homosexual constellations around gay faculty members like Keynes, who was a very rapacious predator on his students. Other faculty members in the group competed with Keynes for the favors of the "cutest" boys, usually unsuccessfully, as Keynes was said to have a certain reptilian charm that he used to great effect. Whatever circle produced Burgess, Philby, and Maclean was no doubt very similar, but its principal was, besides everything else, an agent of the OGPU, as the KGB was styled in that era. How Feliks Dzherzhinsky came to develop this asset is buried somewhere in the KGB's archives, but it was one of the most successful sleeper-agent developments in history.
3. "Kim" Philby's intellectual and emotional maturation, someone once commented on the few remarks Philby left behind for analysis, appears to have been arrested about age 14. His thought on the equities of international political competition, on politics in general and the place in them that his job (his real job, as a KGB asset) occupied, seems to have crystallized when he was introduced to homosexuality or "turned out". The author's speculation (I can't remember which author I was reading, but chances are it was John Barron, whose two books on the KGB I have) was that each of these men was a case of arrested development, and that the duplicitous lives they led forbade much reflection and thought about their place in the world, so that they led peculiarly unexamined lives.
Thanks for the recall. I had heard that the anti UK/American Homosexual spy ring went higher than the jerks you cited.