It might matter for academic jobs at certain universities and at some VC/Wall St. firms, but that's a tiny slice of the world of work.
FTR, IME academic jobs at top universities are about the least likely places to filter on what university an applicant went to. (There are more effective things to filter on!) There are plenty of big companies in the UK that recruit only from a few universities, though (and not only in the finance industry - many engineering firms do the same, though it isn't necessarily the same universities they target).
Come to think of it, probably the employers most likely to do this are the ones that are very popular but *don't* need much in the way of rare attributes in their employees: they are the ones who might most likely wonder why they should incur the expense of recruiting from a wide range of universities, when they can go to a few good ones and get enough good-enough people.
