I knew the Solar GIS thing was going to come up. Always does. I wish they added a few caveats on that page to stop the map from being taken completely out of context
I should have been clearer, my apologies. The problem is the areas where there are vast amounts of land available for solar farms do not receive enough solar radiation to justify the large economic investment required in moving the country towards solar. There is no ROI in solar for most of Northern Europe.
I am speaking strictly about government-level efforts required to maintain energy security in the UK. Putting solar panel on roofs is a good personal choice, but it falls flat on its face economically because governments can't get the economies of scale engaged that countries like China can by investing in solar farms. Hence my statement that Britain should focus on wind and tidal, not because we can't do solar, but because it's entirely pointless to focus on something that we are clearly so behind in technologically.
By investing in wind and tidal research we stand a better chance to come up with breakthroughs in efficiency that can then be exported to the rest of the world. The developing world is now investing more money into renewables than the developed world. Instead of fighting for the solar industry pie, which will inevitably be split amongst India China and the States, we should instead focus on other renewable sources where we stand a chance to be world's best and not just a me-too. We have enough energy for the foreseeable future to run around experimenting with things the developing world can't. Energy is a business after all.
Completely off-topic, fun fact most solar panels in the UK are facing the wrong direction Also, you'll need 12 sq.m per person because solar doesn't generate electricity at night.
On a second look, it seems like you didn't account for the ultra poor efficiency of solar panel, not all solar radiation gets converted to electrical power. I'll probably run the math when I get home and report back if I got it right or wrong.