"Wellies are um. Boots. Rubber boots or shoes for when it rains. They've got other names, but I've always called them Wellies. Rain boots?" Galoshes, too, but he doubted that the other would have heard that if Wellies weren't familiar.
More the fool, Mister Jones.
In any case, while he poked around for the boots, Ianto helped move sodden shoes up to a higher shelf, out of the way of the water. "Even if you do stay at the museum or elsewhere, it might be in our best interests to stop up where the water is coming in. To keep the things in here dry. If for no other reason than to prevent mold." The last thing any of them needed was a respiratory illness.