Rights of way on property

[Guest]

We live in a terrace and there is a pedestrian right of way for several properties in the row. One of the neighbours has built a 'shed' in their garden, they are now living in it permanently with no planning on it and have let their property out full time, so there are the owners and the renters also now using the pedestrian access.
If planning got involved would they be granted full residential planning on the shed even though the only access is through several properties?

[des8]

I very much doubt they would obtain PP to use a shed as a dwelling regardless of access!