I did a trip to Benbecula from Farnborough in the BAC 1 11 XV919. It must have been late '70s as I don't think I was commisioned at the time, but I was accompanied by 10 cadets from my ATC squadron. The aircraft wasn't fitted with full seating so there was a pallet towards the rear with ballast presumably for trim purposes.
RAF VC10s used to operate in/out of Benson which has roughly the same LDA as Benbecula, so I don't see why one shouldn't have visited Benny, possibly in support of the CRP?(RAF Air Defence Radar Unit established for the Army Rocket Range)