Why don’t the RAF lease or buy some modern, "bog-standard" commercial widebodies as FSAs (Future Strategic Airlifters) to replace the VC10s, Tristars and “DTMA-rented cheapo civilian garbage” in the transport role? There’s more than enough work to keep a fleet of new widebodies heavily utilised these days and they would require far less fuel and maintenance per tonne/km than the current fleet.
Why not just outsource that to Federal Express, United Parcel Service, etc.?