Thanks, I thought this was it, but I've got massive gaps in the list. For example I have entries for:
17/09/2016
16/09/2016
15/09/2016
14/09/2016
05/09/2016
04/09/2016
So that's indicating between 5th September and 14th September I never shut down my computer, which is not true, I shut down every evening.
Actually I'm having other problems with Windows 10 (pro), such as frequent Explorer.exe faults. I'd love to do a clean reinstall, but not sure the procedure since I upgraded from Win7 Pro! Guess I'll have to do a bit of research!