@TimmyS: Ubuntu needs to have the list of installable packages updated before it can see hfsprogs as a valid package to install, so run the following commands and all should be happy.
sudo apt-get update
sudo apt-get install hfsprogs
Once 'hfsprogs' has been installed the creator script is able to mount the Recovery partition in read-write mode, which kind of helps with the copying of the boot files over to it