Hello Ian,
It is possible but we have to do this manually from our end. You need to raise a ticket for support team from
http://support.eukhost.com and let them know that the you need the addon domain to point to a directory at same level as that of public_html
let me remind you that you may have problems in future due to upgrades as this would be customized setting and it will break after upgrades that may occur in future.