OK I have the seats out of the car, seat backs off, how do I get the head rests off without breaking the white plastic support????? 1999 VDP thank you

 

Just pull upwards, it is a ball in a cup.
But have someone support the white plastic bracket to prevent excesive bending.

 

Thank you also I put a little shot of WD 40 in each side and it helped. Very much appreciated.Ed

 

I just re-installed my seats yesterday, it is way easier if you only install the headrests after getting the seats in, more room to wiggle.

Also on mine, the ball at the ends of all the stanchions were wrapped in some plumber-tape (that white stuff).
Still not sure if that is original Jaguar, or someone who tried later to get a tighter grip, but you might consider that upon installation.