Welcome to PPRuNe Mr. Foster
Exit rows shouldn't be an issue in flight - within the limits of what is sensible, if people want to put stuff there it isn't a problem. Sometimes people deliberately spread stuff around to prevent others from congregating and treading on their feet. Come descent, and prep for landing, everything, including blankies, cushions, handbags and newspapers should be stowed away.
Plastic bags? Can't help you there I'm afraid.