If you live in a conservation area, like all the properties in the picture, the council my not allow you to have a box dormer but will let you have a mansard or a combination of Velux lights and small dormers. Here you will need to submit plans for approval and, again, it pays to use a company that knows all the local planning departments with experience in who will accept what. Because be assured, they are all different.
There are seldom many problems when it comes to getting planning permission and keeping within the rules.
Most of our projects don't need planning permission and don't require an approach to the council at all - though some do so it pays to know what you're doing.