I've seen this too on various other forums.
A couple of quotes from the Argos & Homebase T&C's as posted on the other boards.
2.2 The 'confirmation' stage sets out the final details of your order. Following this, we will send to you an order acknowledgement e-mail detailing the products you have ordered. Please note that this e-mail is not an order confirmation or order acceptance from Homebase.
2.3 Acceptance of your order and the completion of the contract between you and us will take place on dispatch to you of the products ordered unless we have notified you that we do not accept your order or you have cancelled it (please refer to Returns and refunds).
and
"While we try and ensure that all prices on our website are accurate, errors may occur. If we discover an error in the price of goods you have ordered we will inform you as soon as possible and give you the option of reconfirming your order at the correct price or cancelling it. If we are unable to contact you we will treat the order as cancelled. If you cancel and you have already paid for the goods, you will receive a full refund."