If you add 10 of these to the basket (£6.00 each):
http://www.ledwarehouseuk.com/LED-Lights-Bulbs.php?lbid=358
...and then apply the "STARTSAVE10" discount code, you will notice that the postage is still showing as free even though the total of the order is under £60.00.
Confused myself now!
EDIT: Should I just be changing "SubTotal of items < 60" to "GrandTotal of items < 60"?