Can we add a third bedroom? (Floor plan attached)

[Wingingthis]

I’m totally clueless and new to this. Could we add a third bedroom and extend the kitchen/conservatory into an open plan living space? How much would it roughly cost/is it even doable? To extend out the back both floors.
Where would the window in bedroom 2 end up being? Thank you!

We could possibly go into the attic, it’s quite large up there - again confused where the stairs would go!

You could split the front bedroom as have two windows. You'd need to create a small squared off area to at the top of the stairs for two doors. Or convert the bathroom and create bulkhead bathroom above the stairs by stealing a bit from one or both bedrooms.

You would take space from the back bedroom to create space to put a staircase to the attic where the third bedroom could go

Depends which walls are load bearing and the width of the space you want to convert to open plan. If you have head height in the attic then great, if not you’ll need planning permission for a dormer. Really you need an architect to survey the house.