Seiko SRPB51K1 Under £400.
I hope they have improved the lume, which in my view is an essential element of competent dive watch. I remember flipping one quickly because it was so bad, a few years later i convinced myself that it couldn't have been as awful as i remembered so i bought another; it was and it was sold on just as quickly.
Back in the day the Nettuno was the base for a popular MKII dial conversion, it was the only way in which the watch made sense.