At 222 there were two adjacent lavatory doors, one labelled 'OFFICERS' and one 'GENTLEMEN'. Grades above MS5 were Senior Officer (?or Senior Manager?) and Senior Executive grades. Presumably only these grades could use the Officers lavatory. And by inference you couldn't be both
There were several different messes by grade; the more senior ones had waitress service and wine (later withdrawn). In my early days there as a lowly MS I enquired of a rather short man whether I was in the right queue and mentioned my grade. I'm 6' + tall, but, when explaining I wasn't senior enough for that mess, he still stooped when addressing me to make sure I know I was inferior.
I worked with several ex G.W. men. One of them was a CO4 with first class travel on the ex GW; he was also in the GWR Pension Fund, which had been closed to new entrants long before. However, the surpluses were mounting up, and this was redistributed to the shrinking number of members.