So, we were recommended a very good architect, all the qualifications, experience, feet on the ground, etc. Nice guy. We told him what we wanted, he visited the site, put all his expertise into it. And suggested, let's say, this:

And we liked it, kind of, but it wasn't quite what we expected. So I sat down of an evening, got out the plans, found a pencil with a rubber on top, found an old ruler I must have had in school, protractor, the whole bit. Went through it room by room, reworked it, redesigned it, knocked down a wall, rebuilt the wall, yadda yadda blah.
I ended up with this:
Of course, the fireplace is no longer connected to the chimney, but I feel I've taken ownership of the project.