What Roger said…
I would never have even considered doing that with rear end in situ.
The rear end is a brilliant design. If you require rear brake calipers no doubt you require much more servicing.
The mantra of preventative maintenance over if it ain’t broke don’t fix it has served me well in all my years of Jaguar ownership since I was a kid.
Jack up rear, be smart/safe. Remove rear wheels, place jack beneath diff. Disconnect driveshaft, brake line, and 2 bolts at each corner within wheel arches and you’re done. The entire unit simply drops down.
Now ALL is right there before you. Remove the cage and take care of everything.
It will ALL be DONE for a very long time.
Repack bearings at hubs, replace diff main seal, replace oil, clean out the diff perhaps too, etc…It really won’t take long at all, and you will not have this opportunity again so just do it all and go over everything.
Just lay everything out so you know how things go back together. Especially those thin shims on the brake disks. Just ape them together with masking tape and mark them so you remember. You can see them on above photo.
I’ve done it myself, alone, and replaced it alone, and I’m no whiz.
Took me a couple days as I’m a patient guy, and paint needs to dry.
As a note, for me, POR15 is my dear friend. Paint the undercarriage there and wheel wells.
With cage off those large, heavy lower arms are there free and easy to clean with a wire brush/steel wool and paint with a sponge brush.
Up to you if you wish to paint the “pumpkin” (differential) …but I would at least paint the cage with spray black rustoleum.
This is what I would do.