*If I was the CFN and the building wasn't listed than I would probably have done something similar because it's easier to ask for forgiveness than to ask for permission and access to the courtyard could significantly increase the value of my home so might be worth the cheeky risk.
In this scenario I would get together with all my other neighbours and find evidence of the original building and of any doors leading into courtyard and use that in a planning application to have all the flats fitted with doors leading to the garden in a suitable style.*
Newdaddie, I can't work out if you're joking, stirring the shit, or completely deranged serious.