GameStation is selling "Heroes of Mana" for the Nintendo DS for £9.99 + £1.00 Del.
You can get cashback from certain sites, but check they offer cb on software (e.g. 5% from TopCashBack making it just £10.49)
Next best price seems to be £17.95 from ShopTo.
While investigating rumours of an impending invasion, you discover that you are the unwitting agent of a plot for world domination. Forced to choose between country and conscience, you must embark upon a mission to prevent war.
You assume the role of Roget, a soldier of Pedda, on a reconnaissance mission with his companions. Your aircraft is shot down by the enemy and abandoned by its carrier. This is where you and your crew realises that the mission was a plot by their own superiors to eliminate them, with the invasion of Ferolia just the first step towards Pedda's domination of the world. Witnessing the atrocities committed by the Peddan army, conscience gets the better of you, and Roget and his colleagues are forced to take steps to thwart their own countrymen.
Developed exclusively for Nintendo DS, Heroes of Mana breathes new life into the World of Mana series by taking it into the realm of real-time strategy, a first for the series. As a stylus-wielding commander, you must plan your strategy to guarantee victory on the battlefield. Commanding your forces on the touchscreen, whether gathering resources or marching into battle, is a boon, and you can challenge a friend in head-to-head multiplayer and compare your performance using the Heroes Rankings thanks to the Nintendo Wi-Fi connection.