@drj thanks for that. Not quite sure what I'm going to do about it yet, but that's got some useful options for me to try.
It seems the nvi in Mint's package manager does cope with non-ASCII characters (as I've just installed it and opened a copy of your notes to see how it handled þ)
(I might well have been an emacs user, had whoever installed it campus-wide at Lancaster not set up some non-standard key bindings, so the chance for me to get indoctrinated then was lost 
)