wow that looks like a lot of troubleshooting steps.
to be honest i'm quite an impatient person, after doing the steps in my opening post, and then further trying two system restores (both of which failed) and setting UAC back to default (after having set it to never notify previously), I just decided to do a System 'Refresh'. My thinking was that my important files were safe, since I keep them in OneDrive by default and simply make them all 'available offline', and edit those copies, so I wouldn't be losing anything in that respect.
Refresh actually worked flawlessly - my old desktop used to give some b.s. about refresh image not working since I only had an upgrade license to win8 from win7, verses this device being a surface pro 1 which has Win8 vanilla as it's OS. In fact not only did it work to fix the problems with the modern apps, but it was completed in about 10 minutes. I barely had time to make a cup of tea. Very impressed, and the couple of video files or downloads I had made to my local user folder and not to my OneDrive folders were still kept because I had only done a Refresh and not a Factory Reset... #Winning!
Only problem now is that I have to run through Windows Update and get myself back onto Win8.1Update1, and then I need to re-install all my software programs and STEAM games. But I'm thinking that once I get onto Win8.1u1 and install my critical software programs I'll do a custom refresh image before I then install my games and any software that needs regularly updating; that way if I ever have an issue again I can quickly do a Refresh back to my custom image and I won't be so far behind in terms of Windows Updates and Software Installations.
