I see this is a retrospective application. Has there been any friction between you and building control? I know from experience that the inspectors can be bloody minded if provoked, and insist on things they'd normally let slide.
I was on a barn conversion a few years ago, where relations between building control and the owner had totally broken down (example: To a young looking inspector when he arrived on site. "Hello, sonny, holidays are over. Shouldn't you be back in school?)
Caused all sort of problems with the build, such as insisting that a badly leaning stone wall was retained as it is, instead of knocking down and rebuilding, which any sane person would have done.
Was also the only time that my "grandfather rights" to sign of EICs weren't accepted, and had to use 3rd party sign off.