Enclosing side return - access to roof and gutters

[Chersfrozenface]

We have a Victorian terraced house with a side return at the rear, between the side wall of the kitchen and the garden wall shared with next door.

I would like to enclose this for use as a storage shed / workshop.

But how would we then access the roof, guttering and downpipes on the upper part of the main building, for maintenance and repairs? I can't guarantee that we would get permission to put ladders up from next door's yard, even if there were room considering the angles.

Does anyone have experience of this?

Presumably there is sufficient room / angle for a ladder within the side return now?

If you enclose it (you will of course need an additional gutter and down pipe) can it not be construction with sufficient strength that a ladder can be used on the new roof of the return?

I am thinking about doing this too. The other option is to have a polycarbonate roof that can be taken down when repairs/maintenance are needed (quite rarely IME).