Sorry to hear that it is putting you off the car, I am feeling the exact same way but I am pretty sure that I have figured out what the problem is. I believe that it is the electronic steering lock that engages once you have locked the car because every time I come back to my car the noise is there again ( I can make the noise go away by banging the steering wheel and the noise will stay away until I have locked the car). I have bought a mechanics stethoscope for further testing and will report back!