I looked at putting a towbar on my Jazz, but put one on my Yaris instead.
If doing it yourself you can save money by using a generic control unit and patching into light sockets for the signals , I ran a dedicated fused supply for power back to the battery using small plastic conduit under the floorpan cable tied to existing pipes etc.
If paying for it to be done it's probably cheaper to get the dedicated link harness kit due to the saving in time. It's also likely tidier and can always easily be removed if required in future.
On my Jazz fitting the towbar required cutting holes in the ends of the chassis members to
install bolts , I decided to do the Yaris which was simple bolt-on with no cutting.
