Problem with open_basedir? Just deployed to a server which has the following open_basedir setting:

{DOCROOT}/:/usr/tmp:/var/www/vhosts/mydomain.com/httpdocs/


The webroot is at 

/var/www/vhosts/mydomain.com/httpdocs/public_html


and craft is at

/var/www/vhosts/mydomain.com/httpdocs/craft


So all standard however I'm still getting this:


  Could not find your craft/ folder. Please ensure that $craftPath is set correctly in /var/www/vhosts/domain.com/httpdocs/public_html/index.php


Any suggestions please?
The problem here was the URL in the database was wrong. I had assumed that config was entirely file-based but it seems that the config file is dependent upon the database Site URL. It would be great if this could be avoided as it makes deployment between environments so much easier without paths or URLs in the DB.