Further investigation reveals that there is a file stored on the iPod (in my case in /media/Michael%20HEN/iPod_Control/iTunes/gtkpod.prefs) when it is first set up to work with gtkpod, and which isn't changed in line with subsequent changes made in Edit=>Repository/iPod Options.
I edited the .../gtkpod.prefs directly with gVim, and all now appears to be behaving the way I want it.
Further investigation reveals that there is a file stored on the iPod (in my case in /media/ Michael% 20HEN/iPod_ Control/ iTunes/ gtkpod. prefs) when it is first set up to work with gtkpod, and which isn't changed in line with subsequent changes made in Edit=>Repositor y/iPod Options.
I edited the .../gtkpod.prefs directly with gVim, and all now appears to be behaving the way I want it.