Looking into the manual, it seems that there is only one fuse for the cig lighters. The front one works but the back one does not.
Where would I start with troubleshooting?

 

WOW! That was quick . . . have you bought that XJ8 Sport already?

Remove central armrest and cubby box, as well as surround of gear selector unit but, with luck, no need to remove the long console.
Seems inevitable there is a broken wire or connector in run between between front and rear cigar lighters.
Not as rare as you might expect . . . common area for latter day DIY bodges, who may have disturbed wiring.

Cheers and best wishes,
Ken

 

Today marks the 3rd week of ownership..and 800miles haha.

I am to replace the armrest(only the top part that you open, not sure of the term for it so do forgive me) so perhaps I’ll do the steps you’ve mentioned above when my armrest arrives.

Also, unrelated but how powerful should the rear fans be? I can leave the heat on max settings yet feel little to nothing escaping the back.

I’ll provide an update. Thanks!

 

Sequence is (1) remove hinged upper armrest and stay (2) remove the inner box . . . all in manual.
This gives access to wiring underneath for rear cig lighting as well as air ducts underneath.

There are no rear fans on your car. Twin ducts run either side of central console from front all the way to rear outlets. These are rather compressed internally so, coupled with length, are rather low in output. Pls don't be offended when I suggest that you check there are no obstructions at outlets. Again, the manual gives clues to the broad horizontal tab to depress to pop out the rear outlet. Common for the foam gaskets to give up, become dislodged, and block outlet. Even more common, we as owners forget that you must open the vent controls . . . LOL.

Best wishes,