i think you can adjust it from inside the car.
sit in the rear seats and the tail end of the centre console has 2 wee buttons that look like fake rear electric window switches..
1. gently lift them up using flat headed left handed screwdriver
2. that will allow you access to the handbrake
3. using a *i think* 10mm socket you can adjust the handbrake from there.
4. get a cup of tea and drink out of left handed mug and admire your handy work.