I think you might be a bit optimistic at £499 for 2080ti type of power, my guess for £499 you will see a RTX 2080 SUPER SUPER with 8GB not 11GB....basically something that is somewhere between the current RTX 2080 Super and the RTX 2080Ti...but of course that is pure speculation.
Yeah true maybe a bit optimistic there.
2080 Super is about 6% faster than a regular 2080 I think. So probably 10%-15% faster than a 2080 perhaps at £500. Not bad but not great. But as I said the warranty is a major advantage for me personally.
Side note. With a 4690k, playing games like Overwatch, Destiny 2 and other e sport games on a 144hz monitor. Would a 580/1660 super be enough for that purpose?