Adam, have a look for my thread "Stuck in the circuit", there's a lot of helpful advice from various people in there. I got to solo at around, I think, 24 hours or so, around 15/16 of which were circuit-bashing, whilst flying once every two or three weeks. I've now done two hours of solo circuits, and am about ready to start going further afield as soon as the weather starts behaving...
EDIT here it is, to save you looking
http://www.pprune.org/private-flying...k-circuit.html - looks like I was closer to 26 hours by the time I went solo.