Splitting a room

Andybooth23

Hello,

We're currently looking at splitting a bedroom in two. Ideally this would then create a small bedroom, but if not we'd be looking at an office/nursery. The main bedroom is very large and we understand also that we'd need to extend the corridor (floorplan attached) to fit an additional doorway and this would cut slightly into the other bedroom. Also aware the sensible choice would be to turn the bathroom into a decent size bedroom and use the split at the front for a small bathroom but the bathroom was only recently done by ourselves.

We'd be looking to split the room just before the double window. We're in debate also as to whether another window would be needed for this room on top of the side window. Really wanted to gauge opinion on if the room would be big enough, sensible in regards to re-sale and also if there were any other considerations to be made, or any other ideas? Also any rough expectations on cost would be welcome. 

https://ibb.co/ww4Tck5 (Room)

https://ibb.co/zsfJh3R (Room) 

https://ibb.co/2nH1XGJ (Proposed floorplan)

https://ibb.co/Gn1wxXb (Room)

https://ibb.co/MsDnnX0 (Current floorplan)