A 3 bed house with a big master bedroom (12ftx20ft) with ensuite, Bed 2 (12ftx12ft) and Bed 3 (12ft x 7ft).
Or a 4 bed house with Bed 1 (12ftx12ft), Bed 2 + 3 (20ft x 6ft), and bed 4 (12ft x 7ft).
The only way we could turn our house into a 4 bed house is by having 2 long, narrow rooms of 20ftx6ft. I think we'd be better off leaving it as a 3 bed? But what would add more value?