My 2011 XK coupe has a rattle from the instrument panel area when traveling on even mildly bumpy pavement.
I tried to isolate the vibration to the plastic instrument cover, or the trim in that area, to no avail.
Because it is dangerous to be poking around the instrument cluster while driving down the road, I thought it better to ask if anyone has solved this problem, or for directions on what I might search for to correct it.

My Jaguar mechanic friend's advice was simply: " Just turn the radio volume up!"
I am looking for something a little bit more constructive.

 

A 'hard' rattle, or a light one? Rattles that are in the suspension usually sound like they are in the dash area. You stated a Plastic kind of sound, so maybe not anyway.
Have you tried pushing against the binnacle while you hear the noise? Mine rattles there occasionally.

 

Could be some wires or wire loom that moves and bumps against something. Had any work done that could have resulted in wires being disconnected/connected? Poke you head under with a flashlight and wiggle stuff to see if anything makes noises.