Caravan wiring

Hi, a friend from our church fellowship has a caravan, we have a camp that is around 2hrs drive from here, no sparkies even close by, would cost more than the van to get one to come to our camp. My question is, when inspecting the current light switches and GPO, whoever did it b4 used the same colour wires, piggybacked and twisted together to insert into the switch, looks dodgey and unsafe, all vans have RCD at the main power pole.
Does anyone here in this site have a van with the correct wiring setup, so I can replace the existing wires with proper 1.5 electrical wire, and also the correct colour wires, ie red, Green etc?
I know it has been brought up before, and the practical advice according to regs is to get a sparky to check it out, would be nice but nigh on impossible to get one to come to our campsite. Please don't critisize, as I know the implications and the regulations, just need some practical advice, if none is forthcoming, then no problem, will search elsewhere and see if I can contact a sparky for some advice, don't know any so it would be cheeky.
Also does anyone have a 240v multimeter, if so the correct approach to using one would be great, no harm in asking. Cheers from WA