Excise will not allow transfer to 3rd party other then the one with name / cnic mentioned over NOC. The person with NOC shall transfer the car to his name, get paper work completed, only after that vehicle can be transferred to buyer.
You may politely ask current owner to arrange transfer of vehicle visit with him Excise office submit the papers for transfer, once accpeted and receipt is issued under your name & cnic, you make spot payment to seller. You shall be specific to single transfer fee to your name not double back to back transfer which will be substantial amount. WHT etc etc
HBL will not be able to help you as you are not their client who they leased the car to and issued NOC to.