All I need is brains.
It's sorted now. I think what happened was when I loaded the app onto my phone, I must have entered "USA & Canada" and not "International". I got suspicious when it couldn’t navigate to any place “big or small” in the UK.
So I uninstalled the app and reinstalled and it all worked as before – even my points were there in an instant.
I have a feeling that this might be a common problem. Maybe “International” should be reworded as “Everywhere Else”.
Many thanks for your support.