Hi there. The simplest way to extend a property would be by using the Permitted Development rights, which gives you a certain 'allowance' for converting a loft and on the ground floor. Most houses come with permitted development rights unless they're in a conservation area. The planning portal has some very useful guidance with regards to Permitted Development. I would also advise you to ask a professional, such as an architect for some early stage guidance. It may also be possible to use the pre application advice mechanism that most local authorities will now issue formally - generally low cost and with a turnaround time of 10 working days (the advice you get is not made public and therefore only for you to use). Good luck and happy house hunting!