Hi Geoff,
Thank you again for your further response.
First, regarding an email notification of the posting of a reply to an issue - the existence of an RSS option is duly noted, but I actually rather like your suggestion that making the effort to go back to the site and check for replies with the potential that I might spot something that I can help others with - nice response - I'll stick with that :-)
As for the response to dragging PDFs onto a page, as I said, your workaround succeeds perfectly, so I'm quite happy with that. You are of course correct that this bug discovery of mine will never be corrected now, but it's just odd that it has only just surfaced in these last few days - prior to that it never occurred for me.
Best wishes and thank you again.
PS. I'm a many years user of almost all Serif software - until 2014 I actually lived about 8 miles from their Nottingham headquarters - so I have got version 2 of all three Affinity apps, it's just that I'm much more familiar with the older software. I did try the same exercise with Affinity Publisher - but I got irritated by its insistence of adding a two-page spread when I didn't want that as my intention was always to export to PDF and Adobe Reader displays the pages rather smaller in order to accommodate the landscape format of the spread of pages 2 and 3, but with pages 1 and 4 in portrait above and below the spread.