Ok, tried it again and when I load the site it comes up with the following:
Fatal error: Cannot redeclare superhero_set_content_width() (previously declared in /home/paulc841/public_html/documentalfilms.co.uk/wp-content/themes/superhero-child/functions.php:21) in /home/paulc841/public_html/documentalfilms.co.uk/wp-content/themes/superhero/functions.php on line 25