Last fall I installed an Blinder M25 on the M5.
Here are a few photos from the install. The two M25 heads are spaced a little over 50 cm apart. Blinder recommends between 50 and 60 cm between the heads. The distance from the head to the outside edge of the headlights is not more than 18 inches.
The heads were mounted straight and level per Blinders installation instructions. Here you can see a shot from both the passenger and drivers side.
Another shot....

For added benefit, I took some fine steel wool and did a real number on the front license plate. This made it very dull but completely legible. In other words a poor reflector. I then placed a 1/2" thick length of weather stripping behind the top lip of the plate to tilt it downward toward the road. Any reflected light will be directed downward rather than back towards the source.
I also replaced my shinny front kidney grills with black ones to further reduce the reflectivity of the front area of the car.
Here is a shot of the switch mounted to the dash. The control box is mounted under the dash and routed the wires thru the firewall. This ensures the control box stays dry.
Last but not least, here is a shot of my testing device. This helps me guage changes to my setup and removes any BS regarding the effectiveness of a particular setup on my car. I'll post my test results soon.