Still nada
Well i've managed to get the data to write into the database using the "store summary in database" server behaviour (not to be found anywhere in documentation), but still not getting past the cart.php page - always ALWAYS redirects back to itself.
This is the eighth attempt and everything else seems to be working - it just won't complete the transaction.
Here are screenshots from my PC showing the server behaviours in play on the cart.php page, a screenshot of the mySQL database after data was written to it, and the complete code from my cart.php page.
I'm giving up on this extension until I can get some help -this just doesn't want to work for me at all.