Whatever Rovertech provides I would follow, but if nothing easy can be found using existing harness, it's pretty easy to make your own on the LR3.
I ran cables back under the driver side door sill plates (they just pull straight up to come off, and tucked it under the bottom of the plastic sides in the rear, ending near the access panel on the drivers side rear (below the Accessory outlet, that is switched with the key as you noted). There is a spare grommet under the master brake cylinder assembly on the fire wall, just above the deadpedal for the drivers left foot. This can be hard to access on the engine bay side of the fire wall due to another wiring loom directly above it. Optionally, you can go through the steering console boot. Either way, just add a dash of black silicone sealant around the grommet penetration and you are good to go. I wired mine directly to the battery with a fuse block in the line in the engine bay (for easy access). use 12 gauge minimum wire (or better) and use the size fuse recommended by the fridge mfr. Wiring the LR3 is actually pretty easy due to all the plastic panels that simply pull off with space behind to route all sorts of stuff.