Zeek have iTunes credit selling at more then 16% off in £20 and £25 codes, far higher than I have seen on there before. Not much else of interest at the moment but the iTunes caught my eye (and my PayPal balance)
£20 iTunes credit for £16.50 and delivered by email. Same discount on £25 codes too, and occasionally higher still is popping up.
There is a £5 bonus via referral if a new customer, on top of that (so potentially £20 code for £11.50) but I think the 16% discount is the lowest I've ever seen iTunes on sale- online or instore
Edit - £3.45 TCB too on top for existing users