I'm right there, having just bought my first LR Disco 2 and it being a nice '04 HSE, but occasionally my rear end will sit down on one side or both overnight. I'm thinking going through it with the mods you have will find the problem and give me a nicely upgraded and ready for most things ride. I plan to tow on the road, so SLS will be very nice, medium off roading, probably never any rock crawling, but maybe some log jumping as I'm in the SE USA.
Help us out with a walk through on the upgrades because I don't even know where to buy Arnott lifetime bags. I guess the FOB is a dealer only purchase?
Thanks from us "new" owners...excited about my Disco!

 

https://landroverforums.com/forum/#brand-reviews

scroll down to suspension to find arnott if you read the old posting on there I believe the owner has a 10% discount for members

 

My bags would sit down overnight, especially when it was cold.
It turns out the bags were leaking up under the "folds".
The test...
Fully inflated the bags and raised the rear end...
slid under the truck with some soapy water in a spray bottle and sprayed the bag. Any leak should reveal itself with some bubbles.
Arnott bags recommended. Running them for a couple years now.
Relatively easy job, no special tools, a couple hours at most.