Thanks for your reply.
I am a complete novice to Indesign and using under duress, so imagine my workflow is appalling - I'm just going step at a time and looking online each time I get stuck.
The image with the border is the map of Australia that was 'placed' to the 1st layer (base layer) I created - I can't remember now if this was as a PDF or JPEG. After I placed it, I dragged it to fill as much of the working area as possible. But I don't yet understand the terminology (pasteboard - guide - stroke etc) so am possibly doomed until I get some training. If I try and delete the border, the image goes with it. I have then added multiple layers with different labels and text, so if I drag the border of the base layer to enlarge or resize, the subsequent layers and text are then obviously out of place.
Changing screen mode settings between preview, normal, slug etc doesn't eliminate the problem.
Grateful for any help
Chris