I had changed nearly every GX7 setting possible, and 'fixing' it was beyond my skill. Thankfully there's a menu setting just for times like this: RESET. It asks two questions, for basic and custom settings - I said Yes to both and the camera is back to its happy original self.
I can now dive back into my guide-books and menu settings and take my sweet time fiddling with things that really don't need my intervention. For example - I found the Q.Menu could be customized so I did that immediately, without any thought as to what had been set up automatically! This time I'll try what the GX7 offers first, then toy with it as seems best.
I shall need to reset my Custom C1-5 settings - but those were not as I thought I had set them in any case!
I downloaded an e-copy of David Thorpe's 'GX7 menus simplified' book. It definitely helps to have a translation of the Lumix system (any system, really - even for a US product) so with that in mind perhaps I'll walk myself into fewer times where the camera's actions completely mystify me!