Building Control will need to approve the roof structure that is supporting the roof lantern. I suggest that you engage a structural engineer to calculate the appropriate sizes of structural members that will support the roof and the roof lantern. Your designer will submit the building notice and engineers report to Building Control.
If you are adding the roof lantern under Permitted Development rules, you need to comply with the limits set for pitched roofs. In this regard, the maximum height of the lantern should not be more than 4 metres from ground level. It is recommended that you apply for a Lawful Development Certificate to prove that the lantern is in compliance with the planning regulations.