I made the changes to the .htaccess file as you suggested and have managed to get the credit card to work although I was not able to add the https:// to the confim.php redirect, if I did it tried to redirect to: https://https:////www.championnutrition.net.nz/checkout_success.php so here is the redirect line that I have in the confirm.php:
$eCart1->redirStr = "//www.championnutrition.net.nz/checkout_success.php";
This works using a credit card but I have just tested it using PayPal and after making the payment you are redirected to:
and of course I get the following error:
The requested URL /www.championnutrition.net.nz/checkout_success.php was not found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.