I'd be interested in doing one of those DNA tests myself. From my family tree, I know I have a very mixed ancestry.
My mother was born in London, her mother was from Mansfield, however, my mother was a result of a fling between her mother and a man from Puerto Rico (who didn't stick around).
My father was also born in London, but his father was from Poland and fought in the second world war for the Polish army. While my father's mother was from Cyprus (they met in London, where my father was born).
As a result, I'm some weird hybrid, mixed with a handful of different ethnicities, to the point where nobody could pinpoint where I'm from. Although, put it this way, when I grow my beard I wouldn't blame airport staff if they asked if they can check my bags
Having mixed heritage and not looking completely white used to cause me quite a bit of angst when I was younger. People always used to ask where I was from, not in a mean or racist way, I think they were just genuinely curious, but I never knew how to answer that question.
Nowadays, if people ask where I'm from, I just say I have some family from Cyprus on my dad's side (because I'm guessing people are really asking why do you look a bit brown?
) and that usually satisfies their curiosity.