The biggest pool of "mess" attendees was obviously 222 Marylebone Road - hence 3 messes - one for very senior officers including the Chairman , 2 others dependant on grades - say above EG4 , and below (but above MS5) - remember the numbers of officers could be quite modest , for example the Waterloo RHQ ended up as a reservation in the Charing Cross Hotel.
Remember I was pretty junior when all this was extant , so no real experience.
Amused to hear that other perks were provided , including trays of morning and afternoon tea delivered to personal offices for the exalted (or they did at York)
Meanwhile in the real world , one fondly recalls the 222 tea trolley - pushed down the dark corridors by a lady of a certain age , who used to ring a handbell ("bring out your dead" was a common joke , not appreciated) - quite poor tea and a crusted / caked sugar bunker. Other comments on the tea were it was (following military precedent) , it was almost certainly laced with bromide.
Remember - even large commercial organisations fielded senior management dining rooms in this era , and often uniformed attendance. Therefore not unusual.
Do you remember the office wear for "cardigans" (aside from the cardigans )? Also, would this be senior management or all management?
Office based clerical officers - think beige colour clothing. Maybe a "racy" maroon cardigan would add a dash of colour.
Non uniformed managers - say Assistants would get a decent , dark pinstripe suit , some are still in use today. I still have my "issue" overcoat , pass for a funeral director anytime , and supremely warm and still in use for very cold weather.
Still have my supervisors 3 piece grey suit - same as issued to TTI staff , - cannot fit in it for a long time, but retained for nostalgia. Grey polyester tie soon replaced by a plethora of area and business ties.