Blah is selling "The Teenage Zombies: Invasion Of The Alien Brain Thingys!" for the Nintendo DS for £14.43 (inc Del.)
You can get cashback through the usual sites (e.g. 8% Quidco, making it just £13.28)
The next best price seems to be £17.99 from Play. This game was only just released yesterday (Friday 28th)
The Earth is under attack by a horde of Alien Brain...uh...Thingys! Humans, succumbing to ray-guns, mind-control and shiny flying saucers, have failed to defend their planet and let it fall easily into the clutches of The Big Brain and his army of Brain Thingys. The only hope left for mankind is three Teenage Zombies that have arisen from a graveyard disturbed in the invasion. The undead trio ignores their normal human victims in favour of the pulsing pink brains they see everywhere - all the while being lured to the ultimate lunch: THE BIG BRAIN! The Big Brain soon realizes he's overlooked this "Super Race" as they inexplicably resist mind control, are unaffected by ray-gun wounds and devour his Brain Thingy Armies like sweets! He refocuses his efforts and resources to battle the Earth's greatest champions: The Teenage Zombies!
Teenage Zombies uses a quirky style that focuses on and parodies the Zombie genre, as well as 1950s style Science Fiction. This is presented in a comic book style featuring panels, dialogue boxes and story telling. Gameplay involves side-scrolling adventures opening up to stylus mini-games, double-screen boss battles and brain busting puzzle challenges.