Well played around this morning before work with SolidWorks and created a surface model of based on my drawing (the modelling was about 10 to 15 minutes of work).
To get it to look like the photo I had to increase the base of the walls to 1 metre and given them a 5° draft, wall height here is set to 2.5 metres.
Just so I can see what it would look like skinned, I’ve placed a default brick texture over the surfaces of the model.
Now I need to try and get this model into 3ds-Max, which I'll try to do tonight.