Well I don't know much about this, admittedly, but I know two different people who've did music degrees and both graduated recently - one at Newcastle University and the other at the University of Hull. The one at Newcastle was doing diploma level on his main instrument (the highest possible level) with grade 8 on two others, was a real hard-worker and definitely knew his subject well since he got the music prize at all levels in our school yet he came out with a 2:1 from Newcastle. The other guy hasn't even reached grade 8 on any instrument, was always lazy with work and not at all academic (he also only got a B in A level music) yet he came out with a first.
That's just an experience I've observed that would lead me to believe that the "better" the university, the harder it is to get a good 2:1/1st.