I realize that I'm arriving without getting the numbers from the ATIS....
Has consideration been given to use of unpaid volunteer guides? This seemed to work well for the Smithsonian's Restoration Facility for many years, and is in progress for the new site at IAD. The prospective guides attend about 20 class sessions, and another 20 tours following experienced guides, before they are let loose to run a tour on their own.
http://www.nasm.si.edu/getinvolved/volunteer/
One or two tours were given each day and advanced reservations were generally required. The size of tour groups was limited. No fees were collected.
No doubt this scheme would have to be modified to fit Wroughton.
==== Added 2 April ====
All the above assumes that the airstrip to pask / holiday camp people don't get their way.