yep that was it,
I'm guessing that I can apply this method to all the elements in the summary code block.?
Instead of:
<?php echo (isset($_SESSION['eCartCheckoutForm_shipping_street1'])?encryptcustomer($_SESSION['eCartCheckoutForm_shipping_street1']):encryptcustomer($_SESSION['eCartCheckoutForm_street1'])); ?>
use this:
<?php echo encryptcustomer((isset($_SESSION['eCartCheckoutForm_shipping_street1'])?$_SESSION['eCartCheckoutForm_shipping_street1']:$_SESSION['eCartCheckoutForm_street1'])); ?>