Many thanks for you swift reply.
So sorry if I’m betraying my total ignorance, but are you saying then that the issue is basically with the theme and that the table resizes normally in other themes?
I have tried setting the page layout to one column to remove some of the complications with the two column layout, but that’s not changed the situation.
Thank you for the useful information on responsive tables. Unfortunately, coding is way beyond my level of experience, but I might be able to “phone a friend”.
Many thanks,
Katrin