Battlefield 3 - Close Quarters Expansion Pack.
Due for release in June, and will cost £11.99 RRP on Origin.
You can pre-order it through pcworlddownloads and use Voucher code pcgamer20 to get 20% off the pre-order price bringing in down to £9.59. Probably the cheapest price you will be able to get this on launch.
You will be able to activate this on Origin once you have the Serial Key as per other EA Downloads from pcworlddownloads.