Yes you do need Building Regs for them. Skylights do. A new door between the house and the garage will do because it is an alteration that affects fire safety.Imagine a door between two rooms. One room is a garage. The other room is a kitchen. Hey presto!
I don't see why the entire project needs approval, it's daft. For one I could have started the extra bits a year later. I might not have known they were being done. Fine on a second submission, that's what I'd expect. Not that you need building control for them though...
If the BCO is willing to add them to the application you have running for the RSJ then he is doing you a favour.

