Why didn't anyone suggest that you drove someone over to fly a sortie from the diversion aerodrome? Or instructor + student if you had a car with enough seats?
The threat of 'repatriation costs' might mean that another pilot wouldn't have been as sensible as you were.
Pay them for the actual road miles there and back for the ferry pilot and that's it. If they were too stupid to fly a revenue flight back to base, then they should pay for that themselves!