Damian beat me to it.
Hello Neil,
From what you tell us I agree, you should be worried about the wiring. If the RCD has been bypassed, it makes me wonder why, and it raises real concerns for what else may have been tampered with. Is it safe?
The mains wiring in a caravan is not vastly complex and a qualified electrician would not be mystified by how it should be wired, as it must follow the 17th edition wiring regulations and the 12v system should follow the NCC's guidelines on wiring.
Incorrect wiring of both 230V ac and 12V dc can be dangerous.
I must be blunt and run the risk of being accused of wearing a jobs for the boys hat, but if you need to ask about how it should be wired then you should seriously consider employing an electrician to sort it out and certify the mains side.