Good to read more about where some of the conventions have come from.
Given the discussion on Britten-Norman aircraft, I looked up the company history on Wikipedia, and this includes:
"During the 1960s, Britten-Norman were involved in the development of hovercraft via their subsidiary Cushioncraft Ltd;[6] their first craft, the CC1, was the world's second hovercraft".
So nautical connections seem to encourage use of Port and Starboard for aircraft.
In the meantime, I have also remembered at least one place where use of Port & Starboard is common (and why I wasn't dreaming this!): Those perspective cutaway drawings of aircraft that regularly turned up in 'Air International' and aircraft encyclopedias have many parts labelled as either port or starboard. At least two companies produced such drawings: Aviagraphica and WEAL (John Weal?) and all those I have looked at from both these illustrators use port and starboard for items such as navigation lights, undercarriage, wing components, engines, fuel tanks, air brakes, etc, etc. I am not sure where those illustrators were/are based.