I'm "100% English", i.e. both my parents are English, but given the history of our nation, that could mean a million and one things where my actual ethnicity is concerned.
My mother's family were originally French Huguenots who fled religious persecution in the 17th Century and settle in Tyneside (North East England) and became glass-makers.
My Father's family are from Devon, but historically hail from Cornwall since time begun.
Ethnically, I'm a mixture of different types of white with possibly a bit of North African or Middle Eastern in me somewhere.
I have some Celtic traits, such as long middle toes, which isn't a mystery since my Father's family originated in Cornwall, however some of my facial features like the way my beard grows and my cheekbones hint at some North African blood, which again is probably from my Father's side of the family, since the South Coast of England were constantly being pillaged by North African pirates from the Barbary Coast...
When I let my beard grown, and especially in the summer as I tan easily, I've often been mistaken for being Arabic or Jewish or Turkish, to the extent where I've had people approach me as one of their own and start conversing with me in their native tongue, which is always very baffling and quite amusing at the same time, as I've always been drunk or intoxicated every time it's happened.
I once even had some Chavs at a forest party think I was a "Jewish-Muslim Suicide Bomber" and make quips about 9/11 and 7/7 to me, but unfortunately their attempts at racism and humour went totally over my head, since I've never seen myself as anything but English and I didn't even recognise that I was the subject of their remarks, not until they confronted me to apologise for their "jokes", which they though must have really offended me since I was blanking them and totally ignoring their friendly jibes.