Thx Iris. I was just going to reply myself after some searching online: it would appear that the Playstation acceptance of cards is extremely funky:===================
PSN rejects many payment cards that are valid elsewhere for a number of reasons. It is not an accident. It is completely intentional. If the billing addresses of the cards do not match the registered home address of your PSN account, then there is no chance that PSN will accept them. PSN also rejects international credit cards, most debit cards, cards from online banks that have not verified your billing address with postal mail, cards from banks that don't support the AVS address verification protocol; and several other more obscure reasons. If your card does not work, then you have to use another form of payment.
So... forget it. Thx!