All the shelters appear to have been provided with bed frames - two for adults to run along the sides of the shelters, and two for children to run across the back wall. They had wooden edges and wire bases - and can't have been at all comfortable.
Here are some photos of the larger frames, including the maker's marks along the side.
And here are the official instruction that went with them. Click the image to enlarge it.
Because of other commitments, I can no longer add further material to this website unless it concerns a standard or near-standard Anderson shelter that is still in its original position. Please email me if you might be interested in editing this site.