My daughter has my surname mw and her mother are on the birth certifcate I have constant access to my daughter. I have lived away from her since she was 18 months she is now nearly 7, her mother is getting married this year can she change my daughters surname, I have my parental rights which I obtained in court while fighting for access, many thanks

No, she cannot do so without your permission. However, she can use any name she wants as long as there is no intent to defraud. So if the daughter wants to start using her step father's name instead of yours she can do so, her legal name will remain until she is 18 when she can choose to change it.