Managed to do this yesterday. How can i go about fixing it? Can i simply swap the hinge, or will it be a case of swapping the whole box out? Bearing in mind, this is on an S3, so i'd want to keep the quattro silver badge etc.
This is a common issue on the A3. The root cause is a seized damper, which causes the plastic hinge to crack. Removing the pin is quite difficult and you may end up causing more damage instead of fixing it.
If you find a replacement glove box, it is possible to take your chrome trims and put them on the new box.
If I were you, I'd get a new damper and try to glue the hinge before shelling out for a new box. You can then move the new damper to the replacement box if gluing does not work.
To get to the hinge pin I used a Bosch multi-tool and cut away the plastic around the hinge but I only cut the plastic attached to the broken door... this way the hinge was accessible with pliers, pull them out and fit the new door: