I am looking to build a garage at the end of our garden that backs onto an un-adopted, un-made road. Ideally I'd build a 4x6m garage with a workshop on the side approx 3.5x3m. This takes me slightly over the 30m2 limit for permitted development without building regs. What would I need to do to make it legal? Is it much effort or should I just down scale so I fit under the limit?