You will have to have either a British Driving License Full/Provisional or a Machine Readable Passport from some 120 Countries.
If you have one of these documents use the following steps to remove the Audult Bar.
Click on the Link :-https://giffgaff.com/profile/details
A Drop Down Menu will appear.
Scroll down to Phone and call service settings
Scroll down to Allow adult content on Phone.
Click in circle I want to access Adult content.
Enter Document details in Box Provided.
Click I am over 18
You will receive message to say Adult Bar has been removed.
After receiving the email switch phone off and on to prompt the Adult Bar to lift.