ah, but thinking again this 'in' refers to handbooks, this 'at' refers to functions... forget it.

It does indeed depend... I think if you leave out the article 'the' as you have, it changes the use of the phrase so it can be an adjectival clause (excuse my terminology please) - for example At (University of London) functions we often wear our graduation gowns ... in University of London student handbooks they say ... 老鬼

I went to the University of London, and used to say "I am a student at the University of London" and now I would say "I studied at the University of London."

Hmm.. I am not a teacher, and I haven't had English grammar classes since high school (a long time ago), so someone else will probably come along with a better and clearer answer - but to me the first is like your location, if you are a student or not you can say, " I am at the University of London.", but the second would be if you are a student there. You are "in" because you belong to it. "I am enrolled in the University of London."