Backup VPS, redeploy VPS with plesk panel and components

Looking for a fast completion on this. I have a linux VPS with plesk that needs to be rebuilt. It is hosted by Fasthosts UK. I need a full backup of what's on there at the moment. Then it needs to be rebuilt with all the components that are presently on the VPS. However, I would like the latest Plesk panel which is compatible with PHP 5.3.* We upgraded PHP to 5.3.8 recently and it appears that this version is incompatible with the version of plesk on the VPS. We are unable to log into the plesk panel because of the php upgrade (or so it seems). However, we do have root access. All our sites have not been affected so we need to back up the sites and databases and have them reloaded with a fully functioning plesk panel. As I said, this is fairly urgent.