I have finished the cooker box and I am really quite pleased with the outcome. It holds all the bits I want it to hold and it is easy to move them all around the boat. This first picture shows it undergoing a well advised "CaptainParish" scorch test. I have filled the pan with water and heated it to boiling. The handles get warm, but that is all. I can actually pick it up with the flame at full blast, although I wouldn't recommend doing that. So I don't think there is a high scorch risk, but I will keep an eye on that.
The second picture shows it in place over the basin. I have painted it rather than varnished, because firstly I am useless at varnishing, and secondly it is made up of disparate bits of scrap wood, so they look better painted rather than bright
The third picture shows it outside on a cockpit bench, which is where I would place it when cooking. Apart from the risk of CO fumes, the burning meths stinks to high heaven.