2. I had issues with part of the script having run but not all. The script removes virtualbox-4.3 but not virtualbox-5.0. Maybe it should remove virtualbox-5.0 as well before it is re-added so that errors are not produced if there was a previous failure.
3. I had to change permissions (chown -R vbox:vboxusers /media/xx/VMs share) once installed. Then re-set the box php admin user password and re-import the virtual box machines. The permission problem might have been due to fresh install of OMV 2.1 when disk was from an OMV 0.4 installation though.