Many servicemen active in the 60s were aware of the basic tale regarding the stolen C-130. However, the addition of the Chivenor element is a new one to me. I had the good fortune to serve at Chivenor as a "senior pilot" (I assume this refers to either Sqn Ldr or Wg Cdr rank) for two tours (as Squadron Commander and OC Flying) but never heard any whisper of a Hunter involvement. Moreover, Hunters operating with guns armed was a daily event with both air to air and air to ground training a major proportion of the training syllabus. Hunters departing with guns armed and returning with magazines empty was a regular feature of the flying programme and any pilot returning from such a sortie removed the film magazine from the film camera as he climbed out.
As for the "senior pilot" being driven away and never seen again I can offer more explanation. At the end of a tour most pilots flew a final sortie of choice and many chose a weapons practice with guns armed. On return it was not unusual for the pilot to be met by car and driven off (usually to the Mess for farewell drinks) and I find this a more practical explanation for the tale.