Good old shed, best off not having all the timber, stones and leaves on the roof, it just accelerates rot. If the sheets are lifting in the wind get them secured down.
Traditionally it was twist nails, with galv or rubber washers, which you can still get, but tek screws and an impact driver are easier!
If you redo the roof defiantly worth adding a few skylights. You can get plastic/fibreglass to match the profile of the tin, or the old fashioned way was a tin sheet with a frame in the middle to take 2 panes of glass.
The timber and stones were put up there as extra security in gale force winds, it will all be taken away when we replace the sheets.
I wonder if there could be a protection order on any of these kinds old tin sheds, a lot of them seem to be disappearing which is a shame. I guess it would be easy to get permission to demolish them for safety reasons as sheets of tin flying around would be dangerous.
Does anyone know a good place to get sheets of corrugated iron? There is a jewsons near, they might have them.