We're big fans of Professor Layton's handheld puzzlers, and Miracle Mask is a fine instalment in the series. ShopTo have the cheapest price for the game at present, though it has gone cheaper than this before, and ShopTo's eBay outlet often pops this game into bundle deals. Still, it'll save you a few pennies on Argos' price.
You can also buy Professor Layton and the Miracle Mask for £7.84 from Amazon, though you'll have to pay extra for delivery if you haven't got Prime. Cheers Buzz and TheMo123.