What is the max distance from a bedroom to the stairs?

[Orangetapemeasure]

We’ve bought a very long house. We want to add a first floor extension, but it will be a long way from the stairs. Does anyone know the maximum distance you can be from a fire escape/the stairs. I’ve read 18m online but it’s all a bit vague; is that from the door or the farthest point in the room? Anyone know? Thanks.

Windows count as fire exits too as far as I know? My parents live in a long bungalow and in their master bedroom you'd be ages away from a door but plenty windows.

A window that leads out onto a flat roof is OK as a fire escape, I think.

I had a very long railway station, and bought a Chubb fire ladder for window escape.