Found another thread and think I may have got pepper flash installed - in control panel/programs it lists Adobe Flash Player 15 Pepper. It's made a difference as now when I try and play a swf vid in FB I get an error mesg - "couldn't load plug-in".
The Opera plug-ins entry reads -
Adobe Flash Player
Shockwave Flash 15.0 r0
Type: PPAPI (out-of-process)
MIME type Description File extensions
application/x-shockwave-flash Shockwave Flash .swf
application/futuresplash FutureSplash Player .spl