Many thanks for your help jnjroach and GreyFox7.
I scanned for errors and it told me there were some and offered me various repair options. In the end I performed a refresh. Things had really got bad before I performed it - like hanging as shown below ['
This PC - The folder is empty'] for around and hour and a half...
View attachment 3961
I also lost a couple of days' worth of work which failed to upload to OneDrive.
Things
seem to be more or less OK again now, but there is some strange stuff going on - for example when trying to re-introduce a mail account into Outlook 2013 now, the 'Mail' button in Control Panel fails to respond whatever I do. The Mail App is also pretty slow, but nowhere near as useless as it is on my SP1 (do others have this problem?).
If I send the device back to Microsoft, is there an option to upgrade to an SP3 if I pay the difference?