Please try this

Line 186 that says (worldpay.php from the "fix")

Code:
$md5_signature = MODULE_PAYMENT_WORLDPAY_MD5KEY . ':'.$OrderAmt.':' . $language_code . ':' . $order->customer['email_address'];
try this
Code:
$md5_signature = MODULE_PAYMENT_WORLDPAY_MD5KEY . ':'.$OrderAmt.':' . $_SESSION['languages_code'] . ':' . $order->customer['email_address'];
and put a transaction through. It appears Alan has changed the currency language construction higher up in the worldpay.php file but not changed it lower down.