Next job on the firewall was to fit the cabin heat valve. This fits over the large 2" hole that I'd previously drilled/cut/shaped just below the recess box, however there's no way to secure it in place so that you can match drill the holes. You have to just measure and drill. Although I made one small error, and drilled a hole in the wrong spot, it all worked out okay in the end.
With the valve fitted I could then also clamp the control cable in place. I was gong to connect the cable to the actuator arm but decided I'll leave it for now as I might end up shortening it once I work out where I'm going to mount it on the instrument panel. It is very long.