>>12762263University ranking is tricky. There are no right answers, it depends what you're looking for. However, they are pretty good at indicating roughly where universities stand relative to eachother. A university at number 5 is probably going to be stronger than a university at number 50, but not necessarily much stronger than one at number 10.
Academics have their own view of how good each university is. For maths in the UK, the opinion is generally COWI, Cambridge/Oxford/Warwick/Imperial College London (the exact order varies, sometimes it's in this order, other times C > W > O > I, etc.) but this is not often replicated in league tables because the student satisfaction of W/I doesn't match up with the likes of St. Andrews and Durham, which have narrower and "easier" courses.
Plenty of people sperg about precise rankings, but it's not that much of a big deal if you're not that fussy about course content, which unfortunately many are not.
