Just been to the Trafford centre and Zavvi had their 3 month gold Xbox live cards reduced from £15.00 to £7.50....Cheshire Oaks also had these for the same price!
Didn't buy one myself as I have a monthly subscription, but hope this helps someone!!!
Next best price I could see is on play.com for £12.99 but currently out of stock there!
£6.75 using voucher!