Cleaned (but not stripped and repainted as this is for the time being going to be a get it going, rather than a body off full job).
Close-up of the shaft. One of the faces of the reactionary linkage is burred slightly. When putting it back you will find the two upper bolts are most awkward, with the nuts located above and either side of the master cylinder which means both the spring washer and nut must be put on with only two fingers. Disconnecting the front drive declutch arm gives you a little more room on one side.
And back in place. One slight problem, when I went to put the booster back on, it wouldn't fit onto the reactionary linkage which had closed up slightly I think due to the length of pipe I was using to work it back and forth before deciding to remove it. I put a lever in to open it and snap! The rear of the linkage broke off without much force at all.

So now I am looking for another assembly so I can go through the whole fun exercise again.
On the upside though is everything now works as it should and no bleeding of the hydraulics.