Parity with USD at launch, after launch is demand is beyond supply, then higher.
If stock floods market then 5% margin on $499 so roughly £469-£479 best bet, but to be honest if we can only make 5% on a brand new product, for us its not worth our time or effort, hence I suspect reference cards to have USD/GBP parity so $499 be £599, then custom cards will be more expensive like they always are, look at 2080, we hit £599 on cheaper cards, but cards like Asus Strix and Sapphire Nitro will generally always carry some kind of premium.
Of course if NVIDIA move price or release new product that could force AMD to re-think the pricing, but NVIDIA is an unknown, the $100 price cuts won't happen because then 2060 would be under 1660ti so sometimes I laugh at what I read, because a manufacturer has to maintain its stack and maintain its margins, $100 could happen on older 2080 to clear, but anything on 2070 and 2060 would be much smaller to none existent.