For those that may end up in the same predicament this is a radical solution.
On the left hand end of the manifold there is a dimple where the shaft is supported in a drilling, carefully drill into the dimple using a diameter drill that will facilitate the hole being tapped for a threaded plug. Ensure you dont drill into the shaft.
You should now have access to the end of the shaft. Soak in WD40 each section of the shaft where it is supported in the manifold partitions for at least 12 hours.
Take a suitable diameter pin punch and hammer strike the end of the shaft that you have exposed by the drilling process. The shaft will begin to exit the manifold exposing the areas that had been contained within the partitions. You will probably see carbon scale build up which has prevented you from removing the shaft previously.
Using fine grade emery tape remove these carbon scale deposits, then using a suitable diameter rod of sufficient length drive the shaft from the manifold.
Whilst the shaft is removed thread the manifold dimple drilling and install a threaded plug.
Ensure you liberally lubricate the shaft during re installation pushing and pulling it to clean the partition holes.
You will be surprised how much carbon scale you will find has been deposited onto the shaft and into the holes.
I hope others do not have to take this radical approach to what should be a simple dismantling process.