You'll need to have them in the down position, then open the boot, and look at the mechanism under the parcel shelf. You will see a short spring-loaded fat pin going into the headrest chrome arms...pull outwards and turn to one side. Same for both headrests.
Then go inside the car, lift headrests into upright position and then you can pull upwards and out.
Fiddly but once you suss' out the mechanism underneath the parcel shelf, it's a doddle from there.
cheers
talbir