Windows 8 Pro. Looks pretty clear that the closest you can get to a 'clean install' is to run the upgrade, either coincident with the download or later from a DVD, on a machine with XP, Vista or Win7 and choose 'Nothing' when it asks you 'What to Keep'.
All of which will be moot if I can never connect for the download, which is what's been happening for the last couple of hours.
EDIT -
Wrote that before seeing RND's last reply. Makes sense. So the initial upgrade should be run from within an eligible OS and then reformat & install from the DVD? Or once you have the burned DVD & a valid key, you can install on a formatted drive? Sorry if I'm being thick, but how does MS know you've had an OS eligible for the upgrade key once it's wiped clean? Is it coded in the key? If so, why would people be getting error codes & not be able to activate on formatted drives - see this:
If you see error 0xC004F061 when you try to activate
Windows 8, it means that you're using a product key for an upgrade version of
Windows 8 and a previous version of
Windows wasn't on your PC when
Windows 8 was installed. To install an upgrade version of
Windows 8, you must already have
Windows 7,
Windows Vista, or
Windows XP installed on your PC.
If you formatted the drive before the upgrade version of Windows 8 was installed, you won't be able to use your upgrade product key to activate Windows 8. To activate Windows 8, you'll need to install your previous version of Windows, and then reinstall Windows 8.