when installing the quickstart package for some reason the sample content won't install - the install will complete if I deselect the sample code, but just returns to the step 3 install page after trying to install sample content - I have installed the template already and really need sample content to see how first page is configured

I have checked it and it works.
Please make sure that you have no old Joomla files on your installation folder.
Maybe switch back to PHP version 5.4 or 5.5 because PHP 5.6 is buggy with joomla 3.4.5

I am installing it in a sub-directory - my old installation is in the main directory - could that be causing the problem?

sub-folder should not be the problem!

ok - I tried to install in several new subfolders and it wouldn't work with sample content - and running php 5.4.45 - I really only need quickstart to mimic your settings in demo - want to set grid up on home page and looking at quickstart is easiest way to accomplish this - not detailed in instructions - why don't you give my link to download quickstart file you are using - maybe something corrupt in one I downloaded

Send me your hosting panel acces with instructions ( domain and so on) and I will try to setup the demo content.
www.joomlaplates.com/installation-form