The French doors are going on the current kitchen back wall, and they'll be a full size window on the new 'lean too' wall. I can see how currently it's not great for a fire escape, that's why I suggested a full opening window (it's a pretty huge window atm).
This was the council building regs, so I could investigate a private one for a second opinion.
I hadn't thought of a mains detector, I'll see if that is an option. Thanks