Hi Comrav, Thank you so much for responding, very much appreciated. I'll certainly look into Child Themes...although I'll need real inner strength to load another language into my brain :-)
Thanks for confirming Anton, very much appreciated. I did (and always do) a full file and MySQL backup before every update, so I'll have a copy of that folder, just in case. Thanks for confirming.
Bikerdad - I'm sure you can google 'child theme' for more info.
If you have 'tweaked' the code of your website or changed default images, footer text, etc., it may be gone after an update. But never fear - just ensure you do a full backup of your files (via FTP) and a MySQL backup (via your hosting Cpanel) before doing the update. Then just view your website, check for changes and correct them. Best of luck!