never mind. Answered my own question! did have to edit the XML files
This is actually not a great idea, I'm afraid
The VSE team provide a policy migration tool that you can run to convert policies to the new version - I'm not massively familiar with it but I'm sure some other users here have used it.
Yes, we used the migration tool here twice, from epo 3.6 to 4.0, and from 4.0 to 4.6. It worked flawlessly.