I really like the simplicity of these little arched camping cabins. They are available as rentals in the UK. The idea is simply to have a comfortable place to stay indoors while enjoying the outdoors. Some have decks out front and others have wood stoves and electricity. Not all have beds, stoves, and power so be sure to ask if you decide to take a trip and rent a Pod for the night. For more information visit the pod website. I spotted the pods on materialicious first; Justin has been on fire recently and has been posting a lot of great stuff.
Not enough windows for me. I would also worry about only having one exit.