Granny who?

Well that was very confusing! Let me explain.
I have a copy of my mother's birth certificate and she is listed with the name "Unfrith," however when I received a copy of her (granny's) marriage certificate the other day, her surname is listed as "Humphrey." I asked my mother this morning what her mother's maiden name was and she said "Unfrith" - fair enough, I mean that's what it says on her (my mum's) birth certificate. So I asked her if her mother had lived in a certain street next door to her soon to be husband and my mum got a bit excited because they did. Turns out Granny was a "Humphrey" all the time so goodness only knows who the other person was. Actually although the names are totally different they do sound pretty similar so maybe the registrar misheard. I'm looking forward to showing my mother the copy of the certificate because I think she'll enjoy seeing it.