-
Options are IMO:
A. Get a mesured survey (plans, sections, elevations) and then pay a qualified architect to do a feasibility study and go from there.
B. Get a loft company who ideally have a track record on the same street and house type - give them a brief, ask for drawings and then review their proposals very carefully before letting them do any work.
You cannot assess loft projects in plan - you have to consider the cross section - particularly the stairs - Building Regs Part K is your guide here.
It's the fact that the stairs cut in to bedroom 3 where the box thing is that's a pain, as it means they're not that high as you come up them.
I wonder about them turning and then using the small landing at the top for the next staircase to go from.
In an ideal world I wouldn't really mind loosing bedroom 3 to a staircase + loads of useful storage space. But much like my desired mini-rear extension the economics comes into play. 4 beds are worth a lot more than 3 beds where we live.
As 2nd bathroom is a must. It all gets a bit cramped if you have to put two bedrooms plus a bathroom in the loft. Even with a gable.