With a bit of help from a tech savvy member of another forum I finally managed to get file explorer to access the photos on my camera and copy the new ones to my laptop. It's tedious and time consuming compared to getting the Photo app to import them, but at least it works.
I had to set the 'usb connection' setting on my camera to storage, then connected it and clicked on it in file explorer and down a couple of levels until it finally found and listed the photos (which took ages as there are over 8000). Sorting by date and highlighting the new ones then allowed me to copy them to the laptop.
I don't know if this will be any help to anyone else, but I thought it was worth posting just in case.