I was told by a "Jaguar Specialist" that the LNC2160AD module from the XJ8 will control seat movement in the XK8 but it will not drive the heated seats. Otherwise it works. The normal XK8 module for 2003 at least is the LJE2160AB.

I have no idea if this is true but I thought I'd pass it on.

 

Just in case it's useful to anyone, I can confirm that the XJ8 LNC2160AD seat module I bought off ebay for £25 works just fine for the seat adjustment on the passenger seat of my '99 XK8. I have no idea if it would work heated seats as I don't have them. It was a bit of a gamble, but seemed like a good bet given how they look so similar and have the same plugs on them and are £25 instead of £125 second-hand. I did however have to swap the board into the XK8 module case (it unclips in seconds) as the XJ8 seat computer has no studs for the mounting nuts.

Am now able to move the seat forward to let a passenger in the back. And then are able to squish said passenger at the push of a button. Who needs seat belts when you're pinned down that tightly eh??

 

ODDJOB; I have a '99 just like yours. No heated seats. It would be interesting to know the module number you have. Both seat modules in mine are LJA2160AG/XXX.
Thanks
Mitch