Doctrox, you can have an RCBO fitted adjacent to your Caravan switchboard or it may be able to be fitted into your existing switchboard to replace the Existing Main Switch.
An RCBO is preferred over an RCD because the RCBO will provide over current protection for the supply lead and leakage current protection for the installation in one device.
UPDATE: After soaking up all the info you fine gentlemen offered, I bit the bullet and had an RCBO installed adjacent to the switchboard. I priced it first with Laser Electrical (~$400), then went with the local electrical house here at Putaruru ($410 installed).
Thanks for all the help!
