I should put in a word for PPSC in Bournemouth. They have excellent lecturers, their consolidation course (for the correspondence students) really gives you the required focus. Their notes are pretty good, with some room for improvement, but they're getting there.
My course record is 13 out of 14 passed first time and the other %&£*^* exam failed by 1%, (waiting for the result of the resit!) I worked hard but they also worked hard for me, so I'd recommend them.
I've heard good things about the others, but I've no direct contact. IMHO Oxford is where you'll get the best feedback, but they're also a bit of a factory!