I agree that section 75 would not cover you for reimbursement via the chargeback scheme as the payment was made through a third party, S75 is quite clear; in that the payment has to be made direct to the supplying party with whom the contract exists.

Whether you have a case or not to hold Virgin liable for equal liability in this contract depends on many conditions...I would strongly suggest you see a specialist Solicitor who is experienced in contract law, to determine if you have grounds to hold Virgin liable as a party in this contract, this may also be influenced because of the same fact that a third party was involved.