Dear client,
As per your requirement,Attached proposal includes two design options retaining the external walls.Design option 1 includes retaining of existing toilet and designing around it in order to achieve a very economical and effective solution.Design option 2 includes re arrangement of internal spaces in a modern and efficient way.However both the options have living area,study area and basement in common with variation in kitchen/dining,toilet and bedroom spaces.Also attached conceptual views of living and study area to make the design proposal self explainatory.