Tried upgrading to 5.4.2.2 through the dashboard. Unfortunately wasn't able to get back in to site once I had upgraded. Fiddled about in Filezilla and seemed to make it worse. Have now followed instructions on here how to update manually. Did all steps and now get this error message:

Warning: require(concrete/dispatcher.php) [function.require]: failed to open stream: No such file or directory in /var/sites/l/larkenergy.co.uk/public_html/index.php on line 2

Warning: require(concrete/dispatcher.php) [function.require]: failed to open stream: No such file or directory in /var/sites/l/larkenergy.co.uk/public_html/index.php on line 2

Fatal error: require() [function.require]: Failed opening required 'concrete/dispatcher.php' (include_path='.:/usr/local/lib/php') in /var/sites/l/larkenergy.co.uk/public_html/index.php on line 2

Any help gratefully received by this novice. Thanks (might not post a reply back immediately as way past midnight here in UK).