fingers crossed they wont use it but they do have a get out clause if they so desire. From Amazon's website:
"What we do about mispricings
Despite our best efforts, a small number of the more than 1.5 million items in our catalogue are mispriced. Rest assured, however, that we verify prices as part of our dispatch procedures.
If an item's correct price is lower than our stated price, we charge the lower amount and send you the item.
If a product's correct price is higher than our stated price, we will, at our discretion, either contact you for instructions before dispatch or cancel your order and notify you of such cancellation.
Please note that this policy applies only to products sold and fulfilled by Amazon.co.uk."