Construct a flat roof extension with lantern rooflight to the new bungalow

Our intention is to knock down our current garage and use the space to create two additional bedrooms and a bathroom that will be joined to our existing bungalow. This will be a single storey side extension with one additional rear external door and three external windows. In addition we will be relocating our existing manhole cover by roughly 1m to allow for the building work. we plan on building a pitched roof on the extension to match the existing roof.