As far as the cabin was concerned on state visits etc, it would be the main party (HRH ,PP, any other royals. PMs would have secretaries, PAs etc) and the rest of the entourage in the rear.
Royal flights always left from the Spellthorne Suite, not the main terminal! (You can imagine..."did you pack your bag yourself, ma'am?.."!)
Catering very different, with special meals/requests etc.
Security was very tight, dogs on board before boarding, (sniffer, not corgis!) armed police everywhere. Plain clothes chaps queing for cups of tea in the galley before the parties arrived... but everyone very professional and with a specific job to do. Just as you would expect, really.
LL x