installation scripts weren't set as executable. As a Linux geek, it
wasn't difficult to see/resolve.
In the end ( on the second installation ), I simply ran: -
chmod +x /tmp/IL-Setup/PortalExpress/install.sh
and used that script to start the GUI installer ( rather than going
through the Launchpad ).
PS I'd previously used a script to unpack the ZIP files into my /tmp
folder as IL-Setup, IL-1 etc.