For any body following this thread this was the result of the ticket and the process is working correctly now.
The first part of the worldpay payment response page which updated the orders table with the worldpay reference did not work because the hidden form element being sent to worldpay was incorrect for the cartId on the confirm page.
It was set by default as <input type="hidden" name="cartId" id="cartId" value="<?php echo session_id() ?>" />
But should have been <input type="hidden" name="cartId" id="cartId" value="<?php echo $_SESSION["eCart1_OrderID"] ?>" />
The value of the Key column for the Update Record behaviour on the payment response page was incorrect and was changed from
$WA_where_fieldValuesStr = "".((isset($_POST["transId"]))?$_POST["transId"]:"") ."";
$WA_where_fieldValuesStr = "".((isset($_POST["cartId"]))?$_POST["cartId"]:"") ."";
Also the second part of the worldpay payment response page which sends a confirmation email to the shopper and merchant didnt work because the email body was using an email friendly cart display.
The problem is that the payment response page being returned does not have any cart details.
The session is lost, so you can't use any session variables to keep track of data and this includs the shopping cart. So you need to pass information you can use to look up the cart details and use that to create a recordset that you can use to reconstruct the data you want included in the email.
Therefore the email body should be displaying the relevant details from the orders and ordersdetails tables using a recordset within a repeat region.