You need to check the indexes to the Enrolment Books of the Supreme Court of Judicature (J 18). You may search either by former or new name.

Change of Name

Many people who changed their names didn't want to draw attention to it. It is unlikely that you will be able to find proof, but it may be worth looking through local newspapers. You could try contacting your local library to see what newspapers they archive. The Familia website can also help you find what is available.