I've discovered at an irritatingly-late stage in the build that I didn't pay enough attention to my research photographs of the real building and I've had to do some retrospective hacking.
I came to appreciate that I hadn't cut two of the windows at the rear of the house the correct shape.
The one on the far left needed to be enlarged all-round and the one on the right needed to be a rectangular rather than square, and also shifted a mil or two to the right.
Fortunately, as I have written recently, styrene is a very forgiving material but it is very awkward indeed to try and cut holes with any degree of accuracy into an assembled box, especially one where the walls are 60" thick.
I think I have just about got away with it though.