GAL/LDAP for Entourage/OSX

We’ve a problem whereby Entourage cannot access the GAL, since it can’t find an LDAP server, with Entourage configured assuming the LDAP server is the same box as the DC for the site (which is also the Exchange box).

It isn’t.

By default, MS puts the LDAP server for a site on the same machine as the DNS server, though they’re not very clear about this.
To find out the settings for a particular site, on a Windows box hold down and click on the Outlook icon in the system tray and select Connection Status.... The dialog that appears gives you the Mail, Directory and Public Folders servers.