Last year, we wrapped up renovations on a ground floor maisonette flat in Mortlake SW14. Previously a two-bed, two-bath home, we built a side return extension, transforming the living space and adding an additional office/guest room, en suite half bath, and walk-in pantry. We also renovated the two existing bathrooms and the entrance hallway. We didn’t engage a separate architect for this project, opting to design the extension in-house under the guidance of the structural engineer. The planning application was…