Yesterday I started to pull off the rear liner - only got 1/2 done, but it worked fine. First, I took off the rear boot sil and then the left-hand panel. And what was there? Good news, not much!
My thinking is to fix the battery and compressor (and relays, fuses etc.) behind here, leaving the boot itself for the drawers and stuff that you use.
From here, the plan is to run new wiring from the main battery, which of course is alternator charged to the DC to DC charger, which will then feed into the Lithium battery to drive accessories. I've ordered 5m of 6 B&S with 8mm lugs on each end for easy connection which should arrive next week. I think I'll run this from the front engine bay down the door sils to the rear depending on what I find. 6 B&S will support 50amp plus, so it should be fine for keeping the Lithium battery topped up.
Luckily, from previous attempts, I had the trusty liner removal tool. See below - easy to find on eBay, Amazon or wherever.