I bought this case in Argos 3 months ago for £14, you can imagine how gutted I was when I spotted it in the 99p store! I have seen these cases in two different stores around Birmingham so I have no reason to believe that it isn't a nationwide deal but who knows. There were plenty in stock and lots of variety.
I found leather cases for the nano, classic and touch and also silicon & acrylic cases for the Touch. All cases are top quality and at this price it's possible to get a spare for when the first wears out :) Happy shopping!!