First of all, this is a very useful contribution Kenneth - thanks.
Hate my first post to be so insignificant....but catalogincludesmodulesorder_totalot_tax_gst.php has some extra white space before the opening php tag, this can throw the "warning: cannot add header information...." on the final phase of the purchase process. I just took this out and everything is working great.
I am just starting to play around a bit with this product and getting into PHP/open source community (after years of supporting MS Commerce Server...don't get me started). This really is a first rate product, and the community seems very helpful and supportive. Hope I can contribute something soon.
K