I did try this once. I was looking in the freezer for the Sunday joint on the Saturday night and somehow left my creme egg in the freezer drawer.
Remembered it about a half hour later and went to rescue it. Then decided, for some reason, to attempt to microwave it so it could be warm again; so then I could eat it. It melted. But I had though to put it in a small dish, so I still managed to eat it all up anyway :)