I don't know how you managed to miss this during your university career, but there are absolutely tons of clubs in every university. Sports, political, hobbies, music, etc. Nothing to do with drinking, apart from maybe a once or twice yearly optional social night.
There are 400 clubs registered at the OU student's union:
https://www.ox.ac.uk/students/life/clubs
Including compsoc, which would have been a way to meet your fellow CS grads:
And a competitive computer security club:
And they're just the ones I found by searching computer.
You could've packed your calender with different activities meeting new people every night and never have felt the need to drink a single drop.
After all, you are not interested in these things narrowly and specifically. You just would like to hang out with like-minded people that like to have fun in these sorts of ways.
In these societies, you mostly end up with some specific 'serious' activities (e.g. a talk, a lecture, a discussion, or something competitive). And social engagement then happens separately, usually at a social in a pub, also as a 'targeted' activity. It is a good way to get more serious about your interests, but does not seem like a natural way to make friends.
For example, in fresher's week, 'default' organized activities were clubbing every night of the week. Sports achievements were celebrated with ceremonies, pub parties, chalk drawings on the walls of the college, publications in the magazines.
There is nothing wrong with any of those activities, as has been mentioned that is just what some loud teenagers getting a taste of freedom like to do. But you would expect a top academic institution encouraging other tendencies to even out the social 'hierarchy' a bit. The very fact that 'you might not have noticed the studious ones' who were 'hiding away in their rooms' is the problem when it is happening at the top academic institution in my view.