PLEASE CHECK YOUR ORDER!
Mine showed £2 off through to final checkout, however email confimation showed full price. Rang customer services free phone 0800 1571577 and they said because it is discounted already, code does not apply. However they immediately said that they would refund the £2 taken.
Complained that code (the code is even resent on order confirmation) doesn't say anything about already discounted products. They agreed.
I said they might get a few calls today!!
Sorry, posted in good faith

and code went through all the way to checkout. They are honouring it, but you might have to call them.