The nearside xenon headlight on my 07 plate A6 2.7Tdi Avant S-line has gone intermittant. It works 9 times out of 10 but every few days it fails to light and i get a dash warning. Switching it off and on brings it back on. I have checked that the bulb really is not lighting and it isn't just a faulty error message. Has anyone alse seen that before ? If I need to replace it I know it isn't going to be easy. I found some instructions in an A4 forum for replacing the xenon bulb by removing the water reservoir and power steering reservoir. Is that going to work on an A6 ? Thanks in advance for any advice.