They used the box for sleeping in during the day and they hibernated in it during the winter. We put ours under a large shrub, but if yours like the bamboo area then put it there. Your boxes look much better constructed than mine, so they'll probably be queuing up for a viewing. Put a trail camera there so you can keep an eye on visitors.
We were on a narrow single track lane and I wanted kerbs laid along the length of our site to stop runoff from the road. I didn't ask anyone for permission and just got a company in to do the work. That was in 2015 and they just used a couple of signs.
We used a fire retardant meter board, which is all that is supplied off the shelf.
https://www.cef.co.uk/catalogue/products/1939242-24-inch-x-12-inch-flame-retardant-meter-board
https://www.tlc-direct.co.uk/Products/TLFB2418.html
When we were building our last house we had one window attacked by a crow which left blood on the glass and sill. It happened every day and in the end we had to hang string netting down on the outside to keep it away. It did work though and I think it is usually a temporary problem at this time of year. We have a lot of jackdaws where we are now and they've never been a problem.
I would go for A2A if it was just up to me, but we will have a new oil boiler. I guess you have a gas boiler at the moment, and if that is the case, I would keep it if there were no problems with it.
I've been looking at similar units. These are two of the companies I've looked at.
https://nextdayrooflights.co.uk/collections/flat-roof-skylights
https://skylights.co.uk/product/pitched-roof-skylight-400-x-1500-mm/
All I can say is that, when I recently insured my old house, with a new company, one of the questions was about the percentage of flat roof compared to pitched roof on the house. I don't recall ever being asked that question before.
In March we had only 10mm total, and in April we made up for it and had 122mm, although most of that fell between the 15th and 19th. Our total for the year so far is 358mm, don't know how that compares to the average for North Cornwall.