https://workshop-manuals.com/vauxhall/astra-j/brakes/park_brake/repair_instructions/electronic_parking_brake_control_module_replacement/
This is the salient bit: good luck!
Release the electric parking brake using manual release:
1.1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle .
1.2. Remove the tire and wheel assembly. Refer to Tire and Wheel Removal and Installation .
1.3. Remove the rear wheelhouse panel liner. Refer to Rear Wheelhouse Panel Liner Replacement .
1.4. Remove the rubber plug.
1.5. Using a square tool with measure 3,2 mm (1/8 in) release the tension of the cable.