Like alot of other deals, you can get a cheaper memory card by using the PC world price match policy.
Take a print off of the £7.99 card at play.com, then take a print off of the £18.89 one at PC World. For good measure I take the price match policy as well.
The Difference is £10.90.
This takes 10% to £1.09
£7.99 - £1.09 = £6.90
Good deal to go with my other post.
Hope it helps!
Now only £6.99 @ Play - thus pricematch price at PCW = £5.80