Leisure battery

[AC-T3]

Just wondering were people bring the wiring from their leisure battery back into the cabin.

With a T3 its easy - the starter battery lives under the drivers seat, then I have wires tucked on the side down to under the rear seat where the Redarc relay lives.
From there, I run back along the side to my leisure battery that is strapped to rear of the passenger seat base / pedestal.
From there to my fridge.

With the bay, I assume everyone mounts the leisure battery on the passenger side in the engine bay................Redarc on the fire wall?.................but where do you drill a hole to get the wires back in?

Like you, the T3 all happens under the drivers seat. A 100ah battery lives under the rear seat, and a Redarc and fuse box and stuff under the driver seat drives it all. Including the solar input.