In a weird coincidence it turns out that the company behind these cards (ssp.uk.com) is one of the largest supporters of the Railway Children Charity. Last year alone SSP, and their staff, suppliers and customers helped to raise £100,000.
Back to the card - you simply apply for it at this site. It takes a couple of weeks to arrive in the post and then you can use it at mainline railway shops like The Pasty Shop (a life saver to late night train travellers who've had one too many to drink), The Camden Food Co, Ixxy's Bagels going right down the fast food chain to Burger King.
I've used my card at The Pasty Shop loads of times and sometimes their Chicken & Mushroom pasty tastes like the best food in the world. Other times just the smell of one of a hot pasty will make me want to heave - so sorry if it's had that effect on you.