This is something I've always wondered. The indigenous people of the UK island are the palest of skin in Europe. I think to some extent skin pigmentation is related to hair and eye color. Yet compared to the darker skinned (relatively speaking) Scandinavians and Baltics they have darker eyes and hair. I noticed that in the UK it seems like the most common hair color is mousy brown. With a fair bit of redheads, dark browns and blacks and blondes, but not an enormous amount of them. Go to Scandinavia or the Baltic region and everybody it seems is blue eyes blonde hair, despite having darker skin than the UK people.
The reason why the UK has the most redheads is because of the lack of sun exposure they get on the island. So why didn't more people develop red hair? Why didn't more develop blonde hair? And light eyes as well?