Flymo Compact 340 lawnmower: fold-down screw?

I have an irritating little problem with my otherwise-ok Flymo Compact 340 wheeled electric lawnmower. Two orange plastic flanges on handle assembly are designed to unscrew from their screws in order to release the two sections of the handle so that the upper part can fold down for neat storage. One of the orange plastic flanges has jammed onto its screw; i.e. both the flange and screw are twirling around together instead of one coming away from the other. My guess is that the inner thread of the plastic bit may be damaged - hence the jam. The outer head of the screw is practically flush with the handle and therefore impossible to grab a hold with e.g. pliers. Does not stop the machine from working, of course, but soooo annoying that I cannot tidy it away into its little Winter corner. Any ideas of how to loosen a bit of jammed plastic?