Apple have just announced their latest 4.7" iPhone. Confusingly they are calling it the iPhone SE, even though they already had an iPhone SE which was a 4" screen. I'm looking at it as an upgrade to the iPhone 6s 128 GB from September 2015, so the comparison only covers that screen size.
Most of the data in this chart is from Apple's comparison page. CPU and battery specs are from the relevant Wikipedia pages. The historical UK pricing at launch was obtained from the Guardian. DXO Mark and Geekbench scores are from their own sites.
Bold text is used for improvements.
Since the iPhone 8 did not launch with a 128 GB option, the choice would have been the 256 GB option at £849 so the iPhone SE (2nd gen) at 128GB at £469 looks like a good deal.