@Anthony, Triodos just announced an ethical UK Current Account, and one of the features is:
…an eco-friendly contactless Mastercard© debit card made from natural plastic using renewable resources. We believe this card has the highest environmental credentials of any offered in the UK.
The card is made of an environmentally responsible alternative to traditional plastic such as PVC. This highly innovative new type of card material has been put through a rigorous testing process to confirm its suitability for use in a regularly handled debit card.
So it seems there are some options. Something for the next batch of cards? 
