I retrofitted mine. Takes about an hour as you have to cut about a 2" hole for the lever spring mechanism to fit through into the sill. I used a couple of rivnuts like Nissan to attach it, as self tapping screws will loosen over time.
The cable runs under the rear seat and then behind the passenger rear trim (3door) to the fuel cap door (no lock version). It then carries on through to the boot. You need the associated boot locking mechanism. This also is the switch for the boot light, so grab the wiring and light from the donor car. The boot light hole is hidden behind the right hand side arch carpet.