I worked [briefly] on a 1971 TV series called "Budgie" [Adam Faith]. We shot part of the title sequence [where Budgie's briefcase opens and 20 Pound notes spew out] at Radlett. In the hangar which included a Jetstream [with Astzou engines ISTR] the security man said that Radlett was used as a location for "The Prisoner" some years before [1966]. Based at Borehamwood the Production, under Bernie Williams would more likely have used nearby Radlett than distant Bovingdon. Bernie Williams was an ace at spending as little as possible to achieve good production values. Rumour had it he wouldn't give you the steam from his porridge.......
My bet would be for Radlett.