Instead of buying a shelter, I made one
I said here that I'd buy a small shelter. I ended up building it. It's a polystyrene transport box, lined with cardboard inside, wrapped in plastic outside so it doesn't take on water, with a small hole in one side and straw in it. Over the entrance I taped a tray to work as a porch against the rain. It stands on four paving blocks, well off the soil. It cost me the price of the straw. There are two shelters in the garden now: this one at the front of the house, the wooden one still round the back. What's left isn't up to me — they have to decide to go in.