I set it all up and I am quite pleased with the results. however I discovered that the selection of 6mm allen keys I have vary from 5.97mm (the one I measured to get the size of the broach) to 6.05mm which will fit but gets a bit stuck as I made the broach 6.05mm so I might need to make another nearer to 6.1mm.
I have included pics of the setup and end result but my phone is struggling to get a decent close up of the hex itself.
One thing to note is to do with setting the tool, I found it much easier to set when I drilled a slightly oversize hole (6.5mm) in a plate and put it in the mill then turned it by hand and set it until the plate did not move when turning the broach tool rather than trying to clock it up on the lathe.