In Scotland, any person is free to change their name if they wish to.
You can make this change official and your birth certificate will show both your old and new names. If you are over the age of 16 you don't need parental permission, but if you are under 16 you do, in which case, a parent or guardian must make the application for you.
You can get an application form from any registrar's office in Scotland. Completed applications should be sent to the National Records of Scotland:
National Records of Scotland
Change of Name Unit
General Register Office
New Register House
The fee for recording the change of name is £40 plus £15 for a new birth certificate. If more than one person in the same family is applying for a change of name, at the same time, then each subsequent application is £10