All good points and thanks, the shoulder is now not perfect but is far more functional than pre-surgery and pain free, which is nice.
I'm putting together an aide memoir for Advanced Posting and Scripting in which I hope to incorporate the hard to find nuggets of information with which everything seems to fall into place.
I now have the basic drilling cycle finished and working nicely, understanding the terminology for Clearance, Rapid and Top of Part planes helps a lot so I drew myself a diagram.
Siemens, BCC GUI and BCC POST variable terms all differ, with the one exception that Siemens use the variable reference_plane for Top of Part and in Posting BCC use reference_plane for Rapid Plane