We will see in a few months time, but I suspect even a 1170 will be closer to £500 than the 1070 ever was at launch. Nvidia have a dominant market position and they know it. They also know that there are thou do, if not tens of thousands of people that will buy their latest card at almost whatever price they release at. Enough people have bought Titan Cards in their various iterations in the past for exorbitant amounts of cash for a minimal improvement for NV to know people are waiting. Nvidia might try and see how far they can push it, complete with 'we're sorry, poor yields and rising memory prices have forced us to raise our prices, it's not our fault' while reaping the cash. I still expect even the 1170 to be around £500, most likely more. The original 1070 FE launch was £399 two years ago, prior to the major memory shortage and mining boom. https://forums.overclockers.co.uk/threads/nvidia-gtx-1070-wanna-pre-order.18734903/
I don’t look at pound value as there are many things between what nvidia set their price as and what they end up costing us here in the end. If you want to know how much nvidia have actually raised price by you need to compare 1070 and and 1170 dollar price. My guess is $50 extra at most. If they hike price any more they will get a load of bad press and likely do long term damage to themselves.
With Intel now coming into the game too, Nvidia need to be careful and not **** gamers off. They have done enough of that already and I personally would not hesitate to sell my G-Sync monitor and move back to AMD or Intel in a couple of years time once they can offer 4K gaming performance cards.