Just to add further to this, if I remove the file advanced-cache.php (which the error code is mentioning) and also the object-cache.php file, then I can log in to the dashboard however my website displays the following errors in the header both in the dashboard and also live on the website:
Warning: include(/websites/123reg/LinuxPackage23/ox/an/ad/oxanadodon.com/public_html/conservatoryonlineprices/wp-content/advanced-cache.php) [function.include]: failed to open stream: No such file or directory in /websites/123reg/LinuxPackage23/ox/an/ad/oxanadodon.com/public_html/conservatoryonlineprices/wp-settings.php on line 58
Warning: include() [function.include]: Failed opening '/websites/123reg/LinuxPackage23/ox/an/ad/oxanadodon.com/public_html/conservatoryonlineprices/wp-content/advanced-cache.php' for inclusion (include_path='.:/usr/local/php52/share/pear:/usr/local/php52/share/php') in /websites/123reg/LinuxPackage23/ox/an/ad/oxanadodon.com/public_html/conservatoryonlineprices/wp-settings.php on line 58
Warning: Cannot modify header information - headers already sent by (output started at /websites/123reg/LinuxPackage23/ox/an/ad/oxanadodon.com/public_html/conservatoryonlineprices/wp-settings.php:58) in /websites/123reg/LinuxPackage23/ox/an/ad/oxanadodon.com/public_html/conservatoryonlineprices/wp-includes/option.php on line 568
Warning: Cannot modify header information - headers already sent by (output started at /websites/123reg/LinuxPackage23/ox/an/ad/oxanadodon.com/public_html/conservatoryonlineprices/wp-settings.php:58) in /websites/123reg/LinuxPackage23/ox/an/ad/oxanadodon.com/public_html/conservatoryonlineprices/wp-includes/option.php on line 569
What can I do to get rid of this issue?