So today, I decided to work from the other side of the two sheds. The main reason for that was because the second shed still has its slate roof under all the overgrowth, but I suspect the timbers underneath may not be too sound, so I really don't want to try standing on it
Currently, the doorway into that shed is blocked up, partly with ivy, and also with unmortared six inch (15cm) thick concrete blocks, which means I can't inspect the underside of the roof. I'll decide when I have everything cleared away whether the roof is sound or not.
If the roof has to be removed, I hope to salvage the slates themselves without damaging them. If they're not going to be used to re-roof that shed, they may come in useful for repairing the roof of the old cottage (which is also slated). Although I have a number of slates that I rescued from the other stone shed that could be used for the cottage.
Here's a photo I took of my progress just before dusk this evening, in which some of the slates are now visible.