My house is approx 13 years old, part of an estate. Every house has French doors instead of a window in the main bedroom on the first floor. No balcony or anything. This means you can’t really have the window open at night so I’d like to change it something I can just open a little without worrying about a dog or DC getting out or someone getting in. We had someone to look who advised it is possible but there might be rules about what we are allowed to do, and how it has to look. How can I find these out?