If you have the receipt for the card (which you can use to get a replacement if you lose the card itself) you could take that with you, it has all the details on except your photo. Alternatively you could just get it posted down to you.
photoshop one up and claim it is a scan... if you are a girl some cute smiling would not go amiss...
Quick update. On the train now about 1 hour away from my destination, Edinburgh. The ticket inspector didn't come in to the coach for the first 4 hours and then when he did nearly everyone was sleeping so he just left us in peace. Don't think he was planning on checking anyway. If I'd known this would have happened I wouldn't even have bought a ticket!
Here's hoping he doesn't ask in the last hour of a 5 hour journey!