Hi Ractors,
Yes, my site is now working.
I was able to get a hold of the company who hosts my site.
They informed me that it seemed the theme version was incompatible with the latest WP update.
I was then able to download the new theme version (which had only just been created), send it to them. They then updated the theme via ftp and the site works perfectly now.
Thank you again for your help.
Kind regards,
R