The bare cut plywood was already generating a lot of splinters and I had originally intended to varnish the box, but what I had was green paint and that's the reason it's the way it is.
All the parts were assembled in the PSU compartment and connected as per the diagram. In this first version I've used clips but more reliable connections might be made by soldering them. The 12V power supply was screwed to the inside of the box with 8mm long screws.
The mains PSU has insulated connections but ideally should have an full insulated cover fitted, which I will do when I can find a source for this size of socket.