I have a 1960s chalet style house with dormers. Behind the front wall of the dormer is a vented space which makes the room very cold. I have accessed the void by cutting through the wall. It’s pretty tight and I’d like to insulate the walls of the room from behind the plasterboard. Could spray insulation be an option here? Can’t see it being an issue but there are lots of horror stories. Wriggling through with celotex doesn’t appeal!