I think the existence of the Horizon scenery also had a lot to do with the troubles with ORBX England. Before I got on the ORBX bandwagon in the states, I had been a long time Horizon user with all of the many addons from some very talented developers. As Spud said, when ORBX England is compared to default it is much, much better. But not necessarily so when compared to Horizon VFR plus 3rd party addons.
I watched with great interest to see how a large group of simmers who had many dollars invested (Horizon is expensive) in the Horizon VFR scenery plus addons which represented the finest photoreal flying experience available at the time and may still be the best. Many areas had autogen hand annotated onto the photoreal images from third parties etc. And, of course, VFR London X did a great job of 3D photo real in the city. In the end, it became a battle of photo real terrain plus 3D objects in many areas vs. photo similar but not real terrain plus 3D objects in all areas. Many users decided against ORBX England because they had gotten so used to what the terrain looked like for real.
Here is a video link that someone made comparing ORBX England with Horizon plus the addons so you can see for yourself keeping in mind the video used Horizon areas that had lots of 3rd party addons to give it the 3D objects.
https://www.youtube.com/watch?v=AW7uTh_oFiEYou can see from the comments below the video how some viewers went Horizon and some went ORBX. I think this battle definitely had a major effect on the success of ORBX England. But, that is just my opinion.
Rod