How to remove giffgaff adult contents with no id
To lift the adult content block to access 18+ sites over mobile data, You DO need to be 18+ and have either machine readable passport OR a UK Driving License (full or provisional) of these documents
The only way around this is perhaps You could apply for a provisional license
https://www.gov.uk/apply-first-provisional-driving-licence As this is accepted, it lasts 10 years and would double up as your ID, you don't need to start learning to drive.
NOTE: - You can access 18+ sites over wi-fi without submitting documents