My car has option 5DC Folding Rear-seat Headrests - I have no idea if the process will be different for cars that don't.
This is done at your own risk and all that jazz. I'm not an expert, just an idiot with access to the internet
- Towel to wrap around the bar
To start, press in the release catch on the left hand side of the headrest (1) and pull up that side until you hear the lock disengage (only needs to move 5mm ish). If this ever goes back down, make sure you release the catch again.
Insert the covered prybar between the seatback and headrest (don't start prying yet). To avoid breaking any plastic, I kept the bar about 1cm away from the attachments on both sides (2). Obviously this meant the force was being absorbed by the soft bits, but it's safer and it still worked.
Here's what the headrest legs look like. On the left hand side is the locking leg, which has a single flat groove for the catch to lock into (3). On the right hand side is the non-locking leg - it has a V shaped groove (4). This was hard to catch on my pikey old iphone's camera because of how shiny the leg is so I've messed with the brighness inside the circle to try and make it clear. On my car, this seemed to be the part that was stuck.
Now very gently start to pry, roughly at the points shown below in order A-D, bearing in mind point (2) above. Basically I was trying to wiggle the headrest free by alternating the pressure from one side to the other. It took 3-5 minutes of moving maybe half a mm for each full A-D 'cycle' before the right hand leg popped free, and the whole thing came out as normal. Remember to keep checking your release catch on the left hasn't popped back in - it's only plastic and you'll probably snap it off if it does.
Done I now have an extra inch or so of rear visibility... And as we all know every inch counts The headrest has gone into storage, nothing broken and not a mark on the plastic or leather so I'd call this a success.
Hope this helps someone!