This is about as simple as it gets as far the the work to be performed, it was roughly a 30 minute job barring your skill level. The issue is finding the part, which I have done the leg work for you with a bit of assistance.
I tried finding this using the powering steering reservoir mount bushings as the main search with year and model. But that proved futile over time, so I contacted Dave at everydayxj.com and he said they are probably the same as the A/C condenser bushings from the X300 and got me a part #. He didn't have any on hand, so I went on a search and found them immediately....thank you Dave, your quite resourceful.

The site listed on the bag is to verify the part and for elsewhere in the world to track it down, there's no direct purchase I found there. This sight link (U.S. based distributor)... https://www.eeuroparts.com/Parts/Par...earch=cbc1448+ ...is whom I used and at .61 ea, I bought 10 of them (shipping was more costly) and will probably do my condenser next. All the other sites wanted $2 + each for them and didn't specify Jaguar in the description. If you try to use there Live Help, DON'T!...you won't get an answer (or at least I didn't). I waited over 30 minutes with no reply to the difference of the 2 parts listed in the link, so I went with the cheap one. I'm guessing the more expensive one may have the sleeve included?

So here we are, everything should be explained in pics except the wrench which is a 10mm.
The pain in the butt one is the bottom one, once you get the top 2 loose or off, loosen the bottom one a little and push the reservoir forward and you can get it wrenched to where its finger tight to screw off easier.
Unless you have a boxed end ratchet which should fit and be easier. Those without the CATS may be able to get a socket on it with a bendy.
If you get the idea to clean up the ends of the sleeves with a grinder, remember, these are presized to fit with grommets and you can crush the grommet too far.
NOTE: Don't use the mounting screw to resize the sleeves, you can, and most likely will, damage the threads.