I now seem to be back working as normal.
Firstly, the Now TV App on my Now TV Stick seemed to have uninstalled itself, which made the Home Page look different...... I went to App Store to re-add the Now TV App, it went on, but wouldn't open properly. Turned the Stick off and went back to it a few minutes later and the App would open and things looked more normal....... however, I had to sign back in with my Username and Password to get fully up and running again. I didn't do any software update or resetting.
I've already watched last nights catch-up episode of S.W.A.T so things do seem to be back working OK again for me.