Which block are you in?
The plumbers should have just frozen the pipe from your tap and then put in a valve to isolate that in the future.
My flat has the mains stop cock in the kitchen, however the cold water supply to the bathroom is via a tank on the roof which can only be isolated by climbing onto the roof and into the tank room.
As for your roof, the council won’t know the exact make up. The insurance company you are using is asking daft questions. Find another provider and you’ll be fine.
No provider I have ever used has asked those questions.