The Mesolithic population represented by Cheddar man (https://en.wikipedia.org/wiki/Cheddar_Man) may be the closest we know to the first inhabitants of the British Isles after the last ice age (10k yrs ago). There is evidence of habitation before the last ice age but no human remains have been found. Based on DNA analysis Cheddar man is thought to have had dark skin, blue eyes, and despite his name, been lactose intolerant:

https://www.bbc.com/news/science-environment-42939192