Ok, I've fixed it. For those who want to know how:
1. On the old machien (in my case running Lion) run the 9.3 iWork update http://support.apple.com/kb/DL1563 this should enable the programme files to work with Lion and Mountain Lion
2. Copy the following foldersfiles into the corresponding locations on the new machine (in my case running mountain lion)
a) application>iwork '09 (folder containing keynote, pages and numbers)
b) hd>library>application support>iwork '09 (folder)
c) hd>library>preferences>com.apple.iWork09.Installer.plist & com.apple.iWork09.plist (2 files)
3. open the applications on the new machine and hey presto!