Moving a domain - mapped to a multi site subdomain, back to the domain

Hi

I mapped an external domain to a multisite install and successfully managed to transfer the site using Snapshot.

Due to high levels of traffic, I now need to move the domain to its own hosting however, using Snapshot to backup the subdomain and then restoring to a clean WP install fails.

The issue appear to be with the addressing. After restoring, logging into admin takes me to the multisite subdomain and not the newly restored version which I can no longer access.

Can you tell me if I have missed something and how I might move my site back to standalone installation.

Thanks in advance

Stef