Just popped in to my local HMV (Taunton) and noticed they had both the PS3 & Xbox 360 Collector Editions of FFXIII for £49.99, even when all the pre-order stuff for the game (which is still out in the store) has it marked up at being £59.99.
Standard edition is £39.99 still but with the RRP being £59.99 and the cheapest online price I can find is at thehut for £54 odd.
I haven't bought it myself but I put a deposit down as I want to trade some games in and will be doing so after work today.
Not sure if Nationwide but I'm sure it would be as it is stickered with the normal HMV price stickers.
Deal also available ONLINE (Link Added). Dont forget QUIDCO as well if ordering online to save yourself some more pennies!