Error: There is no release with ID PLESK_8_0_1.
A quick google and I found this: http://kb.swsoft.com/en/2115
A quick read of the instruction on the download page told me that I didn't need a new licence to install 8.1 on an 8.0.x machine "Plesk 8.1 for Linux/Unix does not require a new product license for users upgrading from Plesk 8.0.x versions.". So, I downloaded with latest 8.1 installer with:
wget http://download1.swsoft.com/Plesk/Plesk8.1/Debian3.1/psa_installer_v3.1.2_build070419.14_os_Debian_3.1_i386I needed to make it executable and run it, follow the instructions and I was up and running again
chmod +x installer_file_name