The playstation 3 is £299 at Marshall Ward so if you can get the 20% off voucher to work you should be able to get it for £239.20 + £3.50 postage. Also go through quidco for 6% cashback.
Dont forget to use the promotional code XX214 before checkout.
I have placed an order which has accepted the 20% discount code, so fingers crossed it is honoured. If not it costs nothing to return the items.
Also the extra wireless controller is £34 so with 20% off this works out at £27.20 which is cheaper than I can see anywhere else