alt Hacker NewsI can't speak for the UK, but ... I did my own install of a 6.7kW ground-mount array. The materials cost me about US$12k. That meant just 7-10 years until payback. Sure, I saved on labo(u)r costs, often the most expensive part of the work, but the overall point remains ... it absolutely makes sense, at least in the "right" parts of the planet.
It isn't just the "right" parts. Yes, the UK has less sun but ground mount is not happening in the UK because average dwelling size is so mall. So typically installed on roof of much smaller properties which costs significantly more for far less solar panel. Detached homes are also rarer than the US because of the issues with supply of almost all goods/services in the UK so there are more issues with tree cover. And, of course, almost all the marginal demand for solar panel is through government subsidies which adds even more cost.
Guy I spoke about above lives in a part of the UK with less sunlight, there was extensive tree cover around his property, and the job was done incorrectly (but full subsidy paid). As I said, there is wilful corruption and, therefore, it is impossible to engage with this subject on the basis of rational economic thought. Companies receiving the subsidies pretend to be doing work and politicians pretend the companies are saving the environment.