Ian16th:-
Yes, overseas residents CAN register, but to use their words:
Hi,
Thank you for getting in touch, you can input your South African address and we can get your card shipped out to you. Please be aware that our card is only for offers in the UK, apologies for any inconvenience,
Kind Regards
I've heard that BA are addressing this anomaly and that the discount should be available soon to those who hold the card but are travelling from outside the UK. Only a whisper on the grapevine, so no chapter and verse (yet). Just keep checking is the Order of the Day I guess.