Ok an update.

Firstly the issue we had was to do with the module & not anything to do with Google. Google was accepting all our products but the module wasn't generating our full number products. And as mentioned in my previous post the module was working fine since it was installed in Sep 2011.

So in response to Delia's post (really appreciate your work in this thread) I checked to see if we had the latest version of the module. In turns out a newer version was available. After installing it the feed is working fine.

Thank you Delia And if anyone else has a similar problem it's worth checking you have the latest version of this module installed.