Ok, you have to jump through some hoops for this one.
PCWorld are doing a Sandisk Extreme III 4GB Compact flash card for £94.99 online (laughed? I nearly got a round in!!!), however they'll match Play.com PLUS 10% of the difference. Play's price is £22.99, therefore the difference is £7.20 which takes the price down to £15.79.
This price can certainly be totally nailed 100% for instore collection, but the salesperson I dealt with also said they could deliver it for this price too....I didn't argue!
To get a price match, call PC World on 0844 561 0000 & give them the SKU of 554543 & ask them to match Play's price (here it is http://www.play.com/Electronics/Electronics/4-/880501/SanDisk-Extreme-III-CompactFlash-4GB/Product.html
Full details of their price match guarantee here....http://www.pcworld.co.uk/martprd/editorial/price-match-promise