@Richard_W
Does the installer have any need for interaction from an end user? If so, you'll need to do some customisation.
Secondly, the other way to diagnose where the issue may lie is to try and install locally using the command line:
sudo installer -pkg package_name -target /
Change package_name for the name of your installer. If it installs fine, excellent, we'll try something else. If not, looking at your logs may help
Paul