@rockedge , @mikewalsh , @Sofiya , thanks again for all your feedback. I'm not going to be able to get on with working on this before the weekend but I will get back to it then.
In the meantime here's a thought in response to your "alternative puppy" comment, @rockedge.
I will try the alternative puppy that you recommend, for interest's sake if nothing else, but I'm puzzled about how I might have accidentally messed up the $path variable in my Fossapup installation, which is itself only a couple of months old. I haven't messed around under the hood at all and I've added only a very limited number of additional packages and those mainly in the form of @mikewalsh portables. The only other change that can remember making was my initial installation and subsequent removal of the out of date Java package that's available via the puppy updater.
Best regards to all, @ChrisH (not, btw, @ChrisFH )