Sorry to advertise, but I have seen the postings on the lack of climbing walls in north Hertfordshire. We have just finished building one at The Priory School Hitchin -
http://www.priory.herts.sch.uk/information/facilities-for-hire/ and it is available on Saturdays and Sundays for organisations and/ or qualified individuals.
Please contact Tony Foster on 01462622300 ext 204 for further information.