Credit to flipflopfloss for the original Argos spot, but I thought the additional £27 saving - making this the cheapest way to get the PS3 instore from a bricks and mortar retailer - justified this post.
Argos are presently selling the PS3 for £269.99, plus you then get a £10 gift card, but by taking advantage of PC World's Price Promise you could save another 10%, taking the PS3 to only £242.99.
There's even a voucher for free shipping for spending over £150
Link takes you to Price Promise page.
EDIT: As rightly pointed out PCWorld only price match then give 10% of difference, making this only £266.99. I'd misread the price match. Now how do I vote cold for my own deal?!