Found this on Moneysavingsexpert but it is a genuine deal because I got two cards last night..
THIS IS NOT ADVERTISED IN STORE BUT
Buy two £15 iTunes download card in main Tesco stores and you will only pay £22.50 for them - effectively giving you £7.50 extra for free.
You must buy two cards to get this deal.
How did I get it?
I went to Customer Service to check that the deal applied in Scotland as well as England. The lady rang through to the entertainment section who confirmed the deal. The store had loads of the old style gift cards and I steared clear of the new darker green Christmas branded gift cards. Went to the entertainment checkout, confirmed the deal again and then the were scanned through. Will try and post a copy of the receipt.
Believe this is only instore and only applies to the £15.00 gift cards
I think the deal expires on 9th December so be quick.
There isn't any instore signage. You won't see signs of this instore or on Tesco website, and many staff don't know about it SO DO NOT BE AFRAID TO ASK.
See image of receipt at post no. 35.
Please note the image is $15 but card in Tesco that worked for me was exactly the same colour and style but for £15.....