Most undertakers are OK with the family supplying the coffin as long as they can be assured that it is structurally sound, which ours definitely are. If an undertaker were to object to your supplying the coffin, the only reason I can think of, is that he would be missing out on his profit on the coffin, which is normally quite considerable. If an undertaker did object, I would suggest that you look at using someone else, he is probably telling you that he is out to take as much money off you as he possibly can!