Cheapest its been on Amazon according to the camel, I think they are Pricematching the BT Shop. Asus are one of the best graphic card makers, and if you are after a 1070, then this is a good buy. Be careful as it is massive and heavy. It has pretty cool RGB lighting as well. Free Delivery but only 13 in stock at the time I'm writing this.
Also, you can also use the Amazon Wedding system to get a free £50 voucher if you spend £250 or over. But I would research into that a bit more.