I was in Tesco's today doing our weekly shop and the other half suggested I check the PC section for Cataclysm as it's due out this coming Tuesday. I didn't expect to see it but it was part of the PC Game Chart, labelled as a "Pre-order".
It's the full expansion, not just a code. It's labelled as a Pre-order as the expansion doesn't go live until 23.01 on Monday 6th. I've already added the code to my WoW account and had to download an update when I logged in. My account will now automatically upgrade to Cataclysm when it launches.
This is over £7 cheaper than doing the same via the Digital Download which is £29.99 and it does the same. I would assume this is nationwide as the "Pre-order" price tag looked normal but I do know one friend who was told by his Tesco that it wasn't available.
It was in the Quedgeley, Gloucester Tesco today.