Cannot manage space on iCloud

I cannot manage my iCloud space usage - whether accessing on my phone or via the System Preferences, when I click on the "Manage Storage" link on my phone, or "Manage" on the Control Panel, I get a blank screen.

It's showing that I am using all but 20MB of my 5GB, but I have no way of seeing what that it - I suspect it's left over Backups from the Beta period, but I can't clear that down. (I thought Apple were planning to clear them all down before go-live)

Expect this is a bug but anyone else finding it?