I pre-ordered this tem as soon as I saw it on Amazon. The price was 17.99. Just been on to Amazon again and discovered it's gone down to 12.50! Anybody else who'se pre-ordered this might like to check what they're paying for it.
I think it is Amazon policy that when the price of an item changes they will amend the price accordingly on any items that are on pre order so whilst they originally billed you £17.99 when it is delivered you should only be billed the £12.99.
Of course, if you only ordered the 1 item you could end up paying the full amount anyway as you will not be entitled to free delivery :)