Why wont my wipeout hd game saves work?

I owned wipeout hd fury on disc uk version and had completed alot of the game. I sold it and still have the game saves. I have just downloaded the welcome back free game of wipeout from my us account although im in the uk. My old saves are not being recognised and it is starting me off from the beginning. Is this because of ir being from the usa? And is there a way to remody this?