I gave my 2003 3.5L V8 XJ to my stepson a couple of years ago, at 150,000km.
It did not do too badly in my 12 years of ownership. The thermostat housing is new but just about every other cooling part and hose is till OEM.
Now and again we get it up on my 2 post hoist to change oil or do a minor fix.
My stepson takes good care of it and it does look very smart in a dark metallic blue, it brings on a sense of regret at times.
He has a set of new suspension parts to rejuvenate those items that always deteriorate, ready to be fitted in the near future.
It is still running on the OEM struts but one is leaking and he has ordered new ones all round.

When I gave it to him the left rear door would not work with central locking. He bought a 2nd hand replacement from ebay in the U.S.A.
The X350 and X358 line was never a big seller in Australia so very few scrapped cars to yield parts.
The replacement locking mechanism was from a Vanden Plas, supposedly also a 2003 - but I doubt that was the year.
It is a Bosch item and the replacement one had a moulded in 2 pin connector where the OEM one had a 3 pin connector, otherwise exactly the same.
Luckily I have an electronics business with 40 years of accumulated spares and I found a male and female pin that fitted the Bosch connector one side and Jaguar loom the other side.
I made up 2 short wires with a male pin one end, a female the other and heatshrinked for protection. After checking the function with the mechanism just dangling on the loom, all was fixed.
The only awkward part of the exercise is removing and refitting the clip for the external handle actuating rod.

Now here is something. I have my grumbles about Jaguar engineering at times ( or lack of it ) but I was impressed with the rear door. Having the workshop manual as a guide it was fairly easy to take all the trim off the door and get at things. Being used to flimsy cardboard trims with extra strong grip plastic fasteners like on my XJSs, the XJ trim was a well moulded plastic item that came away with a strong tug after removing screws. The inner water guard was also a well made moulded plastic part. Neat and tidy wiring loom, no sign of corrosion. Good one Jaguar.

 

I have a 2003 X350 and have repaired 2 or 3 doors and the actuators are stamped Ford?

They have a microswitch which wears out but available from Ali Express

 

Maybe front ones are Ford.
Rears ones are Bosch on my 2003 car.
I am a glutton for punishment. I would have pulled it apart to see the problem and a possible fix before buying a spare.
This Bosch unit has a 4 pin connector plus a 2/3 pin connector.
I fail to see why it needs 6 connections, and it is a big piece of gear just for a door locking gadget.

After fitting the new 2nd hand one the lock function sounds like it operates a solenoid and not a motor/gearbox.
That is a bit odd in a way. Solenoids tend to draw a lot of current, but in ancient times cheaper than a motor/gearbox.
Nowadays even cheap cars probably have a dozen small motor/gearboxes for door locking and other things.
They are made by the billion and must be pretty cheap, and draw less current.