Well I've had a reply from Exertis UK, who I'm assuming are the distributors for the Linx tablets in the UK. "Lee" said:
I have been advised to ask you to change the time server that windows 8.1 is synchronised with as the problem is apparently with Microsoft/Windows 8.1 rather than a hardware issue.
Please try the following:
1. Go to the Start Screen, Right-click to get the "All Apps" icon in the lower right of the screen, and click it.
2. Select "Control Panel"
3. From Control Panel, navigate to "System and Security" >> "Clock, Language, and Region" >> "Date and Time"
4. Click the "Internet Time" tab, and change the server to "time.nist.gov", then click update.
5. Check if the correct time is displayed with the "auto DST option"
I did this myself approximately 10 days ago and subsequently the clock on my linx 10 is still accurate."
I have no idea who "advised" him to tell me that...
I'm not convinced by this as one of the first things I do on a new pc is change the internet time server to ntp2.npl.co.uk, and I had already done this two days prior to the time problem occurring, so I think they're off the mark on this. I've also never noticed this problem on any of the other Windows 8 devices I'm using or have used.
I do agree that it's most likely a software issue, but what the actual cause is, is as far as I'm concerned, unknown. Everything I had installed prior to the problem with the clock has been re-installed and the clock's running fine - so far, however if it happens again, which (touch wood!) it hopefully won't, it'll be going back.
It's a nice tablet and beats hands-down in several departments the Lenovo Miix3 10 which I recently tried.