Note: As with all PS4 pre-orders since August 4th, getting your console at launch is not guaranteed. Instead, you will be put in a queue for when stock is available. GameStop are making no promises as to when your console may arrive. They're a big company in the US, less so over here, so it's unclear how much of an allocation they'll be getting. You are saving £20 on the price at other sites though.
Thanks to tomtom838 at HotUkDeals.