Hi Chris,
Thanks for getting back to me, I've been away on holidays so haven't been able to follow up on this. I was kind of hoping that it would have fixed itself over the past week while I've been away but no luck!
I've ran the Wss.Downloader you linked to and I get an Access Denied message when I try and run with the Reset NTFS Permissions option.
Drivepool is properly licensed AFAIK, I get no prompt and a "Deactivate" option when I go to Manage License.
See attached screenshot from the Advanced security tab for the Media folder in the pool.
Thanks for all of your help.
Kevin