I noticed that my ~10 hours in gliders and several powered hours added up to all powered on their noticeboard at BAe.
If you had over 20 glider hours, you'd probably be in advanced. I don't think its that rigid though, ie. if you've got over 20 but haven't flown in a long time there's some room to go basic (or at least that's what I gathered from a guy that was in the same situation on our course).
I don't know for sure though!
