Came across similar problem re low volt light & EASA, fortunately the CAA surveyor managed to find a way of giving approval just using the drawing which comes with the assembly. Don't know how though!
Do you know if this is still a UK requirement only? Seems strange that the CAA can require the fitment of the LV system when the manufacturer doesn't specify it. Sort of runs contrary to the argument that manufacturer's recommendations (seat belts) must now be satisfied and yet they don't recommend this item.