Structural calculation needed for building control regularisation application (UK)

My lower ground floor garage has been converted to a habitable room and connected to the rest of the house by a spiral staircase. A structural calculation is needed to sign this off with building control where a post has been used to support the cut joists. The post is supportted by the foundations of the hosue. I have a sketchup model and photos of the garage showing all of the details, dimensions, specs etc that I have attached.