I do all the CRB checks for my work place - the local high school. Every staff member cleaners, caterers, admin, teachers & leadership team must have enhanced disclosure. 6 weeks is about average for it to come through, try avoiding the beginning of school term-time as all schools will be submitting for new staff members.
I agree with previous suggestions of getting it done via a charity or voluntary organisation. We pay £36 per disclosure at the moment.
Hope you get sorted with it.
Cheers,
Julia