Volumes are improved once plastered. It's important to employ a good plaster. It's best to have roof lights on either side to give a cross view and light. You don't want to feel boxed in at the top of a house. It's worth installing at least 3 roof lights. I would avoid installing ceiling lights in the pitch roof they will annoy your eyes, place them in the flat ceiling, Building regulation will require a mains connected smoke detector.