sorry, one last thing
the billing and shipping addresses displayed on the confirm page 'disappear' if I update my shipping form, as they are populated from the checkout form post values.
The session variables are still there, so...
is the best way to overcome this just to replace
<?php echo((isset($_POST["firstname"]))?$_POST["firstname"]:"") ?>
with
<?php echo((isset($_SESSION["eCartCheckoutForm_firstname"]))?$_SESSION["eCartCheckoutForm_firstname"]:"") ?>
throughout all the fields ?