What is the difference between planning permission and building regulations approval?

Generally speaking, planning rules determine whether you are allowed to go ahead with a building projects and building regulations set standards for the design and construction of buildings to ensure the safety and health for people in or around those buildings.

You can read more information on the Planning Portal¹.

1. https://www.planningportal.co.uk/applications/building-control-applications/building-control/building-regulations/difference-between-building-regulations-and-planning-permission