Well, I ate humble-pie and called on the guy who set it up. (As per the suggestion by boatman61 right at the start.)
In short, I should have listened to the CF posters, as the correct answers were there all along.
Starting with the square shaft handles, these fit the mast
mounted Cleveco halyard
winches, I just did not realise (and stupidly did not try) that a square shaft handle would fit in a star-drive pattern winch. Apparently they can also be used with the jib
sheet winches in the cockpit
. So full points to roverhi, zeehag and Jesse. Thank you all.
The odd ball round tube handle is for the anchor
winch, I just did not realise that you can easily take the top of the winch off to fit the handle, so full points to Dennis G.
Thank all again for your time, the lessons in common sense and the funny
comments. Always a joy.