Thanks for all the info everyone, and for those pics gaijin.
Finally went to use it the other night. The ebay 12mm-8mm lovejoy coupler had arrived from China (my wife thinks that is hilarious too, especially since it arrived in a nondescript brown bag) but doesn't quite fit so we just directly attached the drill to the mill shaft. I think I'll need a 1/2 inch coupler because the shaft is 1/2 inch or 12.7mm so it just doesn't fit.
Anyway we milled about 12kg of grain no worries but there is a small amount of scratching on the shaft so I'll try and find a 1/2inch coupler to protect it long term.
Overall very impressed with the Millmaster compared to the old Marga. If anyone is new to it and is attaching the plastic hopper, you have to remove the metal guard which the hopper replaces. That had us fooled for a few minutes.
We disintegrated the grain to be honest, so probably need to adjust out a little, but just made sure to stir well and remove any clumps etc during the BIAB process. We seem to have got very high efficiency, I don't have the % calculations but for a recipe that usually gets 29L in the cube at 1046 we got 1054 out of one urn and 1058 out of the other...