Thanks Dewey.

I am actually wondering whether that is the case with William Yemm's father, John Edwards - ie that he was actually a John Yemm, but brought up by Thomas Edwards and named Edwards.

Or that he was born John Edwards, but realised his father was a Yemm and not Edwards.

You are right - they are certainly a mystery! I thought it was going to be so easy with an unusual name, but how wrong could I be!