All these people saying what they give their children without context of loans and accommodation is meaningless. I could give my child £100 a month or £300 a month and say he's ok with that - but that does not mean anything as you don't know what loan he gets or what his accommodation costs are.
I suppose the more useful thing is how much a student needs after accommodation costs.
Students may get a maintenance loan - and that amount depends on the parental income. I think it comes as a surprise to some parents that they are expected to top it up.
So assuming accommodation is paid for (either via loan or from parents), what amount do parents think a student should need per week to get by? Once you know an amount you are happy with, then look at the amount they get from the loan company and figure out what you need to do to top it up - and if they need to work as well
Of course, there is the argument that the loan amount has not kept up with inflation and rent increases.
Which is why knowing what you think is a reasonable amount a student needs per week (after accommodation) is a better discussion - and that amount is not necessarily what you give them as some of it may come from the loan and any work they do.
(DS and I are about to have this conversation in September)