I am currently looking for the lowest price of this card from all online shops, ebay, real stores (every place you can buy it from).
I am in London.
So far the best price I've got is 21 pounds on Ebay.
I really don't think there's a better one, but you are the specialists. Try to beat that.
P.S: Vouchers, disscounts and bulk buy (no more than 10 cards) accepted.