Actually just spent 15 mins on phone to Apple Support, and during the call I solved it!
The issue was that I had purchased iWork as a set of disks before the App Store for Mac existed.
As a result, the serial numbers of my disks are not stored on Apples servers - so no automatic update.
Going to: http://support.apple.com/downloads/#iwork
Gives the updates that you can do the old fashioned way...
Apple have logged this as a problem for all those who had iWork or other applications pre-installed on a new machine or who bought disks with iWork or other applications on..
Those who have downloaded Apps from the App Store should have no issues with updates... the rest of us who either pre-dated the App Store but have the Apps loaded - will for now have to seek out any updates and manually update them..
I understand that there is a request internally at Apple to ensure the servers recognise the "non-App Store Apps" and include them in the automatic update, but they are probably waiting until the download bandwidth for Mountain Lion calms down a bit before working on this..
Hope that helps a few...