I've now got a permanent enclosed set up and have today closed the greenhouse doors to the outside.
2 x greenhouses, glass roof, glass front & back - against the garage anyway, and wire mesh sides.
Greenhouses were both free off a local selling page, and DP had the wire mesh already so the set up didn't cost me anything.
Hens are fine in there, plenty of light & fresh air, but dry and no exposure to wild birds. They still all just stood there clucking at me in disapproval when I shut the doors though.