A kind Oxford Admissions tutor (Head of Admissions) told me that research quality isn't really relevant at all, it's just a way for unis to get higher in the rankings and look better to undergrads. Of course they try and make it look relevant by saying things like "This means you'll be taught about all the new advancements/stuff we find out etc.." - though this is extremely unlikely to be the case. Furthermore, he said that a good research quality kind of goes against/clashes with good teaching quality and a Uni which actually cares about its students - since if they're busy researching they're not teaching/concerned about what their students are getting up to.
Obviously, I'm not saying a Uni can't possess those qualities whilst being good at research (e.g. Leicester probably) - but when it comes down to it judge a uni by many other factors first than research quality.