Thank you for the photo and the bit of a description. Of immediate concern is the fact you have two pairs or brown and blue wires which are of course normal mains (230Vac) colours. Because I cannot check first hand to see what they are connected to I have to urge absolute caution and do not proceed unless you are certain of what you are doing.
A pair of green and whites should go to each water tap and when a tap is opened, a micro switch inside the tap should close its contacts to allow power to pump. So all the greens should be connected together and all the whites should be together, so if any tap is opened it should cause the pump to run.
The DIN plug should only go between the heater and its wall switch. 12V Power for the heater is connected inside it's wall switch, and not down at the casting
Because of this uncertainty I'm not prepared to guess at what any of the wires are, and I urge you to only proceed if you are competent and confident working with electrics. Otherwise it would be best for safety to arrange to have the caravan wiring checked and put right by a qualified fitter.
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