I've returned the Launch function at end of installation.

With help of Yvan at Mac Scripters who put a script together for icon adding which works in Mavericks, I'm over half way there. It works with the user selecting source and destination files of the icon. I've reduced it down to user select source. With any luck I can get it to do it automatically. (I can achieve it if I know the location of the the source as this has worked in testing. If I can't script it to find its present position then I may install a temporary dummy file with the icon & remove it at the end. A sloppy approach I know.) If I can get it working all the way I'll try adding it to the installer script or alternatively calling the script from the main script (the call part works.)