to the forums!
These cars aren't super cheap to own, but they are far less expensive than many other German cars.
leibniz and I share the same experience, I had the brake light circuit warning on my OBC, and merely checked and replaced any bulbs that weren't spec bulbs=problem fixed.
As for coolant low, if the warning is on, the sensor probably works fine. I would check the level when the engine is COLD, not after you see the OBC message. It is probably a little low, just remember to fill with BMW coolant mixed 50/50 with water. This is very important as one of the few problem areas of these cars is the cooling system. The BMW coolant is phospate-free and is highly recomended to use nothing else.
I would offer the same advice for the license plate as stated above for brake light