Thank you @t-p and @joyously
So I’ve looked at the error log and I have found my next clue. It seems to be indicating a plugin called ithemes-sync. (Not sure this is even a necessary plugin.)
Here’s the error line:
overtonphotographicclub.co.uk [Tue Aug 13 16:40:50 2019] [error] [client 37.76.132.194:0] PHP Warning: require(/home/sites/4b/9/99bc265f01/public_html/wp-content/plugins/ithemes-sync/lib/updater/load.php): failed to open stream: No such file or directory in /home/sites/4b/9/99bc265f01/public_html/wp-content/plugins/ithemes-sync/load.php on line 100
Any guidance on next steps (thank you in advance).