I too sailed with Van Ommeren (London), who managed both Medomsley and Crawford Shipping Companies. I knew several personnel who had sailed on the "Langleeclyde" Among them, Trevor Morris, who was my first Chief Officer, and Chris Smith who I believe was an apprentice on her, (later Captain RFA), who told many stories of "good relations" between crew, stewardesses and passengers.
Some of the stories I heard are not for publishing, but it was true that she was a happy ship and gathered that she was a pleasure to sail on!
Not sure if she carried more than 12 passengers though as I don't recall that she carried a doctor.
In my time she was on long term charter to United Netherlands S.S. Co. (VNS) and did their south and east African run.
I joined my first ship, "Crowborough Beacon" as an apprentice at Christmas 1960 in Bolnes shipyard, Rotterdam where she was re-commissioning after having completed "Jumbo-ising". She had been cut in two and a new 60 foot section was fitted between Nos. 3 hold and the midship/engine room section, being named No. 3A hold. The eventual freeboard was very low, something akin to a loaded tanker.