I have a round plastic ceiling rose in our kitchen which I am unable to rotate in order to remove it. I guess the heat from the bulb below may have distorted it, or just made it adhere tightly to the part attached to the ceiling.
I've tried turning it with a (not very good) plumber's wrench, after applying WD50 liberally, but this just slipped round.
I thought of drilling two holes in the flat bottom, inserting screws and using a screwdriver or similar to turn it. Any better suggestions?