So I upgraded to Windows 10. It was running slowly which I thought may be a disc space issue, so I deleted the files for rolling back to 8, assuming there would be a recovery partition.
It was still slow and I was having Bluetooth issues so I tried an 'advanced restart' aiming to find the recovery partition. Realised there wasn't one (or it wasn't accessible). There was an option for Reset so I figured I'd try that. The tablet hung for ages on the Lynx logo and now reads:
A configuration change was requested to clear this computers TPM (Trusted Platform Module).
WARNING: Clearing erases information stored on the TPM. You will lose all keys and access to data encrypted by these keys.
Press F12 or Volume Up to clear the TPM
Press EC or Volume Down to reject this change request and continue.
What do I do?