Initially at Farnborough and later at Boscombe Down
The flight deck crews were drawn from the Met Research Flight (MRF), however there were no dedicated Co-Pilots so Snoopy generally flew with 2 Herc Captains, one acting as Captain the other as Co.
On occasions where people were on leave then MRF would drawn on the main sqns at Lyneham to provide the Co.
It was this way that I managed to achieve so many hours as a Co on Snoopy.