Light is key to every room in the home, north facing rooms should utilize skylights to introduce uninterrupted source of day light. Windows rely on direct sunlight or reflected light, skylight is a constant source of illumination with the added bonus of airiness to the room.
Always resolve problems on paper rather than leaving it to the builder and when your knee deep in mud. Changing the drawing can often be done for FREE, or for a very small fee subject to circumstances, either way it is important that the drawings give the builder the correct information for an accurate quotation and avoiding extras during the build.
Plan for the maximum, and build to your budget. For example, you do not need to implement the entire design, a partial build still validates your planning approval and will not preclude the development continuing in 10, 20, etc years time; in planning law it’s a bit of a grey zone to which no Local Authority to our knowledge has contested.
It is always a good idea to build up a brief of your expectations and requirements to ensure the design factors in these elements. Research your local area for similar styles and materials thattally with your personal taste.