freelander 2005 facelift

Firstly ,good day to all members, have got a 2005 facelift freelander td4,fitted with just a 12n socket,my intention/aim is to fit a fully operational new type 13 pin euro type,have tested the 12n socket and found the only connection available(from socket) is for side lights,further investigation will obviously be required!,now to my main question,im fairly knowledgable at wiring systems,but dont know what this vehicle will accept being connected?by that i mean can the wiring for the basic 12 n functions just be connected to existing and a voltage sensing relay be used for the 12s functions,ie fridge,charging interior light functions etc,--- or do i need to fit a by pass relay as well for the 12n side of things if i find either there isnt one fitted or whatever ,obviously i will also need to fit an indicator warning device,my main beef like most other members is i do not want to have any main dealer costs or programming unless it is unavoidable any advice would be appreciated,by the way all other problems now resolved,i think!new pump and fuel filter fitted,mot passed yesterday.many thanks in anticipation of replies.