I had the same thing happen to me, as soon as it took the money the link in the playstation store started saying "This content cannot be accessed on your account"
I have only ever had one ps3 and one account, it is all based in the uk and uk purchased. I have emailed them aswell so will see what they say.
Peter
---------- Post added at 08:27 PM ---------- Previous post was at 08:19 PM ----------
Phoned the support line in the end, you download it from within gran turismo, new button on far right for downloadable content!