Jamie,
Have you checked the sills? cos 90 percent of the time they rot out as much as the boot floor and rear arches/seatbelt mounts. You can buy most panels but the welding has to be 100% to pass the MOT, expecially the seat belt mounts and around the body mounts.
Paddocks do the repair parts but nothing fits as per LR specs. Lots of jigging, lots of lifting up and making tools to hold the body so it does not flex. Its not a job I would wanna be doing done it once on my dads M reg disco took about 2 or 3 weeks of after work. Its solid now better than new. Don't under estimate the ammount of jig making and body supporting you have to do to keep it anywhere near straight. That was just the boot floor not the inner wings or sills they were ok. Jai