I know young people who have attended/are still attending some of those.
BIMM (mostly know of the Manchester campus.) I know young people currently studying guitar performance & songwriting. It's OK, they are mostly doing well but standards are varied.
ICMP - no first hand knowledge
LMA - the one person I know left the course. (drummer) They said standards were low and it wasn't good.
Bath Spa - no first hand knowledge but I have heard good reports from people on a group I am on.
Waterbear (my knowledge is of Sheffield) Young person I know there (drummer) is doing really well, great course, he has progressed a lot and is getting lots of work too. I have also seen some of their other students perform and am quite impressed. No reason to think that Brighton is any different to Sheffield. Heard good reports of Brighton on a group I am on.