I just replied to a similar post here:

https://www.jaguarforums.com/m_30556..._/tm.htm#31236

You can only add a single din stereo, but no-one sells the fascia adapter for the X308- only the X300 '95-'97

I have installed a flip out monitor to my XJ8 with not fascia as of yet.

To install, you need to first remove the [leather] gear surround, just lift it off (it is held on with clips). Then undo the four bolts, you should now be able to remove the entire centre console veneer trim. This will expose screws that hold the orginal stereo and the climate control unit. Undo the screws (one on either side and the stereo should just pull out.