I fixed it myself - I found that it only affected my windows account and not the rest of my families.
I created a new account and...
Flash is 'built in' in Edge
I'm having this strange problem in later driver releases:
When playing YouTube videos in fullscreen in Microsoft Edge, my computer freezes....
OS: Windows 8.1 x64 (fully updated)
Card: Sapphire Radeon HD 7870 Ghz edition
Native Resolution: 1920*1080
VSR Working: No
I have uninstalled drivers / used DDU. No VSR option here - weird that they would state it as supported but not implement it properly :/
VSR doesn't work. Even when turned on by EnableVSR, which works for me usually :/