[himar2468]

But you're claiming an Invalid code, and not anything pertaining to non-delivery.  

Have you told them this, and why they're denying It based on Irrelevant Information?

According to the paypal rep I have just called, he said with codes they arent actually covered by paypals "item not as described" after explaining to him that the code is as described but is invalid he said it still falls under the "item not as described" category. As long as the buyer can prove that its been delivered then the dispute automatically closes in their favour. Should I just charge back through my bank?

You can certainly try a chargeback, but weigh up whether It's worth doing so. If It were a high value Item, yes.

thanks for the advice^^