I can't say for sure if this is a nationwide deal, I found it in the Portsmouth store. On a shelf edge that had dvds such as Fantastic Mr Fox & Invention of Lying for £7 there were a pile of the Chipmunks bluray/ DVD/ digital packs. By far the chepest price for it. It's £17.91 on Amazon and other places seem to be around the same.
Alvin, Simon, and Theodore meet their musical match after returning to school and entering into a battle of the bands competition in hopes of saving the school's troubled music program. Sent to live with Dave Seville's younger nephew Toby (Zachary Levi), the three lovable marmots decide that getting an education is more important than belting out pop tunes. But the school's music program is about to go belly up, and the only way to save it is to win the 25,000-dollar prize in the upcoming battle of the bands. Though the Chipmunks are confident they have the songwriting skills to steamroll the competition, a newly formed singing trio dubbed the Chippettes promises to give them some stiff competition on-stage. Brittany, Eleanor, and Jeanette are indeed the real deal, and the closer the competition gets, the more Alvin, Simon, and Theodore realize that in order to win, they'll have to give it everything they've got.