As per title. I joined at checkout with my Xbox live subscription and got it for £17.99!
Can use the £10 on ANYTHING though - no minimum spend! :)
(currently £27.99 on offer - £10 voucher for joining)
New customers only.
Other good value options:
2 x DVDs for £8 (currently £18!)
2x chart blurays for £12 (currently £22)
My bestbuy is FREE to join and stores all your receipts for you so if you lose it then its not a problem (according to them anyway).
EDIT: To join you need to buy something and join at the till. Cant just join without buying anything. My purchase was my first purchase and it counted there and then :) Or buy the cheapeest item instore and get £10 voucher if you dont have any luck getting them to reduce the item you are buying.