I have a Peugeot 307 it is a 51 plate. I have a trailer hitch on the back, was there when I brought the car. It doesn't have the electric plug in bit though is this difficult to get?
You should be able to find a wiring kit at any place that handles trailer hitches.
A vehicle specific wiring kit will plug directly into the vehicle wire harness without issue. No wire cutting is required. These are easy to use, but a little more expensive.
Universal wiring kits provide the same thing, except you have to splice into existing wires to make the connections. You will need more tools and have the vehicle wire diagram available to complete the work.