My E46 BMW 320d was recently driven through some water too deep for it. The engine and rest of the car is fine but the electric levelling feature for the headlights has failed. The headlights were in a state of pointing right down to the ground resulting in a very short throw of light from the car. There is a small dial to the right of the steering wheel (next to the dash lighting adjuster) which is used to adjust the headlight angle. This no longer works - when it is adjusted a whirring motor sound can be heard from the headlights but no adjustment happens.
The headlights themselves are standard dual halogen units.
I've temporarily mitigated the problem by adjusting the dial that exists on the top of each headlight accessible from when the bonnet is opened which is a sort of manual override but it would be good to have the automatic adjustment working.
Looking at the headlight units there's no obvious sign as to the location of the motor that adjusts the angle.
What's the best advice to try and diagnose and fix the problem or should I just take it to a professional?