I just installed the Speedline reflector LED's on my 2012 M5 Touring this past weekend:
On the 2012, it was more than just the clips that held the reflectors in place. There is a plastic cover that screwed into the backside of each reflector with one screw, this cover clamps the reflector to the bumper.
Getting to the screw from under the bumper on the passenger side was easy.
Getting to the screw on the driver side was a different story, due to the exhaust pipe and the muffler. You will have to remove the screw blind with a stubby screwdriver. Not easy to get to, but it can be done.
I drilled a 1/4" hole in those covers and added a rubber grommet for the wires to pass thru.
I wired the reflectors to a SPDT Relay to have the bright LEDs on during the day (tail-lights off) and dim LEDs on at night (tail-lights on).
BTW, it didn't come with instructions, but the blue wires power the bright LEDs and the orange wires power the dim LEDs.