There is a REAL 'real' Bounty Island in the Pacific off the south-east coast of New Zealand, at 48 degrees 0 minutes south and 178 degrees 30 minutes east. Whether that is the 'real' real ADVERT Bounty Island I rather doubt, however!
The location that the bounty adverts were actually filmed is a place in Crete called Via. Apparently they chose it because of a rare species of palm trees that grow there. Hope this helps!