There's not a lot to be said about this. Because we used the CBE kit, the way of working was pretty much decided.
A commando socket under the step at the rear of the van is connected via a 2.5mm2 flex, inside a plastic conduit, to a junction box under the main circuit breaker. The junction box was included so that if the cable was damaged, despite the protective conduit, it would be easy to replace.
From the junction box, the mains cable enters the van directly to the circuit breaker, a CBE kit item. The circuit breaker is a dual pole type disconnecting both live and neutral for safety. It's followed by an RCD breaker to cut the power in case of any earth leakage faults. The van has an earth adjacent to the circuit breaker to make it obvious that it's attached!
From the circuit breaker, a feed is taken to a distribution box, again CBE supplied, which runs feeds to three sockets and the battery charger in a star configuration.