You're telling me that a commercial & cultural behemoth on the scale of Glastonbury Festivals Ltd can have no influence on some tin-pot helicopter operator?
The fact remains that travelling by helicopter is not even close to being a sustainable form of transport, admittedly car transport isn't ideal, but it is the only option for the masses, and if Glastonbury is keen to promote sustainability then that needs to apply to everybody who attends, not just us proles.