all 3 of my children bear my surname,the father has to be at the regitrastion when this is done to have the fathers name,if married then afaik its automatic,the only thing with being unmarried is,the father has no paternal rights over his children(in law)any official forms that need signing i:e hospital forms has to be done by the mother,i had this explained to me by a sister on a ward.
funny how that works,your within a stable family unit and the dad has no rights over his children,YET if he was to b.ugger off the govt will hunt you down and make you pay for the upbringing of said children,worlds gone mad.