Adding a new window

[thereinmadnesslies]

I want to have a new window put in downstairs in my house, in a wall that is currently all brick. We are a corner plot and the wall is the side of the house and would look onto a road. I want a clerestory window so it would be at the top of the wall, not affecting privacy. I've tried to attach a picture to show the sort of thing.
Any suggestions who I should contact to do this. Is planning permission and/or building regs required? Do I contact a builder or a window company? Has anyone done similar and would you mind sharing the costs? Thanks

Difficult to say without knowing the exact situation, but I would definitely get planning involved in the first instance, even if it’s just an informal chat with someone. Building regs would apply, but the fitting company should be able to self-certify if they are FENSA registered

Building regs will apply and fensa only covers replacement. The council will inspect the support for the opening and any insulation needed around the edges as well as the window itself.
Planning, usually planning isn't needed for a new window but sometimes they remove that right as part of the original planning permission. Doesn't hurt to ask the council.