why is it being let bills inclusive?
Maybe it's a council flat being illegally sub-let? Bills included means the council tenants name stays on the bills so on official paperwork, it looks like the tenant is still there, when in reality, the resident is a sub-tenant. But the integrated kitchen appliances indicate it might not be a council sub-let.
The other alternative is that it provides cover for people who want to fly under the radar for whatever purpose (illegal, warrant out, criminal enterprise eg brothel, drugs).
Is it a shed at the end of someone’s garden or an illegally converted garage or basement or something?
Flat in a block. Looks like the other flats are quite nice. But that one has been trashed - same condition as a squat.