Hi Will, all have given you good info, I wouldn't worry to much of the quoted above unless they are needed to be done, I have a home made battery tray that is larger than the ARB and still manage to change my filter, yes it's fiddlely, but still doable, save your money for other things, it's 2min to take the battery and tray out.
Also in 262,000ks in my Disco, I have only replaced the radius arm bushes and watts link and I do a lot of towing off road and on road, I wouldn't worry to much about the rotoflex unless your fitting a locker, stock brake hoses are fine too unless they need replacing.
Get a EGT, low coolent/temp and gearbox/transfer temp gauge device, always a good idea if towing, I have one, it's peace of mind to be able to monitor and to know how hot everything gets.
Get airbags with the new coils, Coilrite or Polyairs, much of a muchness. the most important things are keeping the engine and gearbox/transfer cool and suspension, set them up properly and you will be fine.
Baz.

