That's the same type of brake my Series 1 Lotus 7 had. it is much like the Spridget brake, but deconstructed as the stay for the cable sheath is attached to the chassis rather than to the brake mounting plate.
While this would be an excellent part to put onto the XI, the standard brake lever will work as well, but mounted on the right side.
I will go over and take a look at my buddy's LHD Caterham and see what they did with the hand brake on that car.