Do you have the right image highlighted in the film strip that you want to print?
Yes, the filmstrip shows just my image and all others are greyed out. Nothing else is selected
Phew! I found the solution, which was to go into the Print menu while in the print module, go down to "content" and then "choose selected photos" rather than "flagged photos"
I should point out for clarity that I am a pro and have been using LR since before it was made public. I have just reinstalled the OS on my machine and had to reinstall LR. I had no idea this "content" thing existed as I've never used.
Anyways, thank you very much for your support