The kitchen is currently approx 2.5m x 3m, and would grow to 4m x 3m.
the outside wall of the back sitting room (needing French door / conservatory) = 4m
These are rough guesses. But tell you, I think, that the space isn't huge?
I'm thinking of buying a property where the outside of the ground floor (facing the back garden) needs renovation work. A very bad, small 1970s extension is causing damp problems and needs to be completely altered:
(i) removal of outside toilet, and extension of kitchen space to fill new...