Thnaks for this Andrew, but, unfortunately it does not work. I have found a work round. If I copy the images to a USB stick, LR will import them from that. I can then move them in LR to where they should be on my HD.
Not the best, but I can now take more time sorting out why LR import is not recognising images and folders on both my iMac and MacBook Air, both of which have the latest OS, LR and PS versions. I have both LR and PS cleared in the OS security and privacy to access anything so it is not that. I may try uninstalling LR and PS and reinstalling them.
Best wishes,
Jonathan