Recline and console yourself.

 With the rear seats and side panels done, it was time to move on to the front seats.
 Frankly, after I disassembled the stock XJS front seats, I found them quite underwhelming, especially for what was supposed to be a grand tourer. Very underbuilt frames, virtually no support, rubber diaphragms instead of springs, a poorly shaped back rest. The XJ sedans have far, far superior seats....
 Anyway, I had been hunting for a nice pair of used seats that would be supportive, fit in the XJS and not look too modern. As the XJS is only a relatively small car, the backs couldn't be too high, nor could they be too wide, as the XJS has very large sills and a fairly wide and high transmission tunnel and console.
 Eventually I found a pair of series 4 RX7 seats that were complete, looked OK style wise and being from a small sports car, should have fit in the XJS. They also have the huge bonus of having a decent, adjustable lumbar support for driver, adjustable headrests and the passenger seat has a tilt forward pedal for rear seat passengers. Plus, the seats have actual steel springs, instead of the stupid rubber diaphragm, which means extra support where needed!
 They are a perfect fit. Here are some photos of me mocking them up into the car:

As you can see, they were old and filthy, but complete. So, onto modifying the bases and retrimming them.
The RX7 seat base frames were pretty simple, the bases were dead flat in the mounting plane, except for the driver's side inner, it kicked up a bit, to clear something on the RX7 floorpan. I had to make short legs to compensate for that, but the other six mounting points were very close to the stock XJS mounting points. It only required some flat plate about 2" long to be welded flat to the base of the RX7 seats and drilled to suit the XJS tracks, and the tracks then bolted straight on. Very easy.

Bases patterned up and laid out for assembly:

And base with new skin stretched over for a trial fit. Note that I carried the fluting over from the back seat, makes the seats look factory!:

Completed base:

As you can see, the RX7 seat is also very low, as per the XJS seats, so headroom is not terribly adversely affected. I would say the seat cushion sits about 1" maximum higher than the stock XJS seat.
And the pair completed, but without headrests:

Installed in the car, they really do fit quite well. Enough clearance for hand brake, console and the seats with headrests tilt and slide forward without catching the headlining:

So all in all, a great and easy swap.They are extremely comfortable as well.
Next on my hit list was the centre console. I had 3 to choose from, two very early ones and a later one. I chose the later one as it was the least warped. Jaguar stretched the vinyl onto the earlier consoles without using a seam for the contours, and it pulls the sides of the console out over time.
Here's some photos of marking up and the final console. Not too much to comment on, except that I deleted the rear ashtray for a cleaner look:

I also retrimmed the A pillar kick panels. They were fun, the old cardboard was a bit warped, but the relatively heavy carpet I used has flattened and stiffened them up nicely. Of course, once they are screwed into place, they will be nice and straight anyway. I prefer these early kick panels, they have a more custom look than the later vinyl/ leather trimmed ones: