We’re adding a 3m2 porch to the front entrance, within the Permitted Development rights. Do we need Building Control approval?

Building Control approval is not required for the porch provided as long as there is an external quality door and windows between the porch and the main building to control thermal bridging. Any heating or cooling systems must have independent controls. Building Control would only become involved if you were to do some structural work, such as removing a load-bearing wall.