Right, I closed all things down, disconnected from my router, turned off my firewall, turned off AVG (I selected until next re-start) and tried Windows back up again. After an hour and twenty minutes, it completed.

So, I did a re-start, turned on my firewall and connected and here we are.

I suppose OE, you're underwhelmed but after all this mucking about, I seem to have a back up on my external drive.

I dunno if it was the check disk or what it was that allowed it to complete this time. I did wonder if it was AVG that was the problem because last time I tried, when I turned off AVG I'd used the 15 minute setting? Wocher think?