We have currently a local person who has built a number of structures in
his garden.
They range from a casino, bowling alley, soft play area, dolls house, tennis court, badminton court, squash area, bar, cinema. I'm sure there is more.
I actually went round it a year ago as I collected the twin grandchildren from a party there a year or so back. I was amazed what was there. It seemed to go on for ever. The local council are taking him to court to demolish it all. It is not doing any harm to anyone so why?
It's just tacky and horrible. I think people should be able to build what they like underground so there is no visible intrusion but that's just repulsive and very much an eyesore.