Ruth - sounds very much like the School Governor conferences I used to administrate. Only 300 delegate places for over 9000 governors, 13 workshops offered twice in the day, 2+ seminars, surgery and opening and closing lectures, 2 lunch sittings, 2 dozens speakers and VIPs and dealing with technical issues on a rather spread out campus.

It was a bear to organise and tiny in comparison to Sidmouth. Best of luck and as little stress as possible to those organisers.