The above is from a history of United Biscuits (UB) Aviation ( previously McVitie & Price) privately published late 80s by their then chief pilot Dave Ward. I posted it on the Which Aerodrome thread earlier this year but here it is again to save searching.
I managed to get a few flights on UB corporate aircraft while employed in IT by the company 1968/88. Before my time they had Miles Messenger and Gemini, then Piper Apache and Aztec , and then , briefly an Aero Commander before a line of 2 King-Airs and 3 Super King-Airs, latterly supplemented by a Baron and then an F90 King-Air.
Sir Hector would usually pilot all of these himself if not engaged in mid-air business dealings. The southern base was at Denham, convenient for his southern home at Gerrards Cross and company HQ at Isleworth. UB substantially funded the hard runway and lighting at Denham. Mundole, as you say, was near his Scottish estate at Dunphail. I believe they were among the most highly utilised of UK corporate aircraft and, at one, stage their schedule was published around the company so that mortals well below board level could use empty space. These schedules often showed over-weekending at Mundole.
At the time of the book's publication UB had a Starship on order which never happened due to problems with the type and, more critically, the decline and fall of the company after Lord Laings retirement,
.....Doug