Well, Hawthorne was certainly gay through and through. As for Gielgud, not sure - he may have had "experiences" but I had a feeling there was more to it than just that. As for the other two, Olivier was married a few times I think (though of course that's no guarantee of heterosexuality), and I would have said O'Toole was straight.

One sure thing is that gay activity in one's formative years is no guarantee of sexuality. At some UK public (i.e. private) schools such things are practically part of the uniform. An admirable tradition.