Choke control light

[David2021]

I found that there was a water leak and the culprit was the aluminium casing at the rear of the cylinder head. Fortunately my spare cylinder head had one attached. I removed it to see wha sort of condition it was in and it appeared intact. I then removed the leaking one…photos attached I hope. Cleaned everything up, made a new gasket & refitted the replacement…needless to say the choke warning light doesn’t now work!
Oh yes, the heater(?) outlet pipe was a different diameter so I have to make up a replacement closure device, no heater in this car. ( a length of hose pipe suitably plugged!)
I noticed that the block drain tap barely worked, so that will need poking out!
Any comments on how to encourage the replacement casing to work the choke switch properly? It is a different pattern as the outlet pipe is different and stupidly I didn’t take a photograph of the replacement.
Any comments out there?
David