Well, I decided to take a punt on installing it direct from VideoLAN
edit /etc/apt/sources.list and add the line:
deb http://download.videolan.org/pub/debian/stable/ /
Then add their key:
wget -O - http://download.videolan.org/pub/debian/videolan-apt.asc|sudo apt-key add -
Now update the system
sudo apt-get update
And install libdvdcss2
sudo apt-get install libdvdcss2
And suddenly all dvd players start working on all dvds. Cool!