Hi, from what I know, Northern ballet school (which is completely seperate from Northern ballet theatre) is in Manchester. I don't know much about the school except it's where my dd's ballet teacher trained.
NBT is based in Leeds (use to be Manchester, I think) and now has it's own academy, which runs open classes, also has it's own associate scheme and a profesional training program. They also hold summer schools, for which I think are just for students in vocational training (I might be wrong).
I think David Nixon is the artistic director of the company and the academy.