Very interesting when I play around with the light trends where I live from 1992 to the present the light pollution has seen a slight drop, however over the past 3 years it has risen slightly. Recently Caerphilly Council has replaced the sodium and mercury lights with LEDs, they just replaced the heads and not adjusted the distance between the lamp posts, this has resulted in quite a few areas being a lot brighter, we don’t need to put the bathroom light on anymore! We moved here 6 years ago and the light trends over that time frame showed a slight rise which seems to have been reflected in my observations. It makes the CPRE results even more odd.
Thanks for the links, very useful.