Without the proper equipment here's the way to do it:
Park the car in a garage with the bonnet open. Shine the headlamps onto the ceiling and use PVC tape to mark the position of the horizontal and diagonal lines on the ceiling for each headlamp's dipped beam. Then,
without moving the car, change the headlamps over and use the tape marks on the ceiling to re-align the dipped beam.
This is a simple cheat that my dealer told me about before I swapped the headlamps on my old Cooper and it worked perfectly
Tigger.