Thank you so much for your help in fixing this problem. Your advice worked perfectly. The only thing that I did differently was to revoke the existing certificate beforehand.
Could I also add that I notice that you replied to me on a Sunday morning and I am extremely grateful for such commitment. I have spent a lot of time on this issue and would not have fixed it without your help.
I did read the certbot documentation looking for a list of command line switches (-d, -i, etc) which might have led me to the solution you provided, but I couldn't find one in the certbot documentation. I am sure that it exists, but I just couldn't find it. I logically looked at the Certbot Commands section here: https://certbot.eff.org/docs/using.html#certbot-commands, a paragraph high up there would be the ideal place perhaps. Just a cheeky suggestion.
Crucially you fixed my problem and I'm very grateful. Many thanks for your help again.