WARNING: This page is about a different car, the 2011 Jaguar XKR, 2011 Jaguar XK, 2010 Jaguar XKR, and 2010 Jaguar XK. However, it is still accessible from the selected car via links, so may be relevant.
Measure the cylinder block/cylinder head distortion.
Using the special tool, measure the mating face distortion.
If the value is not to specification rework the mating face.