I don't think it will be that bad.
I'm expecting a 3070 with around 2080ti performance for £450-£500.

You forget who is releasing these cards

Expensive cooler, expensive memory, expensive 7nm large die. MOAR Raytracing. I’d be very surprised if they lower prices by that much especially with no competition.
Even 2070S WITH competition was £499. Original 2070 was £599 (apparently).