Unable to access an area of my wall for repair due to downstairs neighbour stucture

C_Noodles

A stone in our wall just beneath the roof is crumbling (we are in a flat - the upper level of an old stone house). The downstairs neighbour has a 'weak roofed' structure (shed/garden room type thing). They are telling us that the tradesperson can't stand on this. We looked into scaffolding but due to the unusual setup of the property this is not feasible either.

Do we have any legal position here - are they allowed to have a structure that completely prevents us from having repairs done - which could eventually affect the structural integrity of the building? 

We are in Scotland.

If anyone has any experience of this, I'd be grateful to hear how you found a solution.

Thanks