My thanks to Dave (davegee) and Jill (jkb) for their detailed replies. After much careful thought, I decided to try Dave's suggestion of partitioning the laptop's drive. His instructions were exemplary. The process really was straightforward. I then followed instructions from a Microsoft Support topic that guided me through the necessary steps to move OneDrive from drive C: to drive D:. I started the partitioning at 11:30am and had OneDrive up and running, and fully synchronised with the online copy by 1:30pm.
Now I'm off to make a celebratory mug of coffee!
This afternoon's task will be to locate and delete any "Z-" prefixed files and folders. These are copies made, over a period of several years, when making significant changes. They existed to give me a quick fallback should a change go pear-shaped. It's high time they were deleted to reclaim their disk space.
Regards,
Peter