I got the e-mail too, but can't download it, it says:"not enough space to save it in the HDD".
It's something similar to the Ratchet & Clank Demo download problem, which was easy to fix just copy about 500MB of anything to your PS3, and it works, but with God of War not. I have an European account, but don't live in Europe.
If anyone finds a solution please let me now. (sorry for my English)