The NIMBYs (or even worse, the BANANAs*) will object to pretty much anything and everything. The only reason anything ever gets built is that the planning authorities have guidelines to follow, and don't just do what popular opinion says.
Bearing in mind that when roofs are used the generation is usually not exported
That's a big assumption. The sun's just come out here, but I'm at work. So most of what my panels are generating is being exported to the grid. The strange way in which FIT and export payments are calculated means that I get paid the same whether I use the electricity myself, or export it.
*BANANA = Build Absolutely Nothing Anywhere Near Anybody
S P Barker BSc PhD MIET