please check your cars cabin air filter. it is suposed to be changed at the 10k check up. I did it all miself to save hundreds of dolars and saw the horror!!
The compartment is located behind the pedals on the drivers side (US version) there are two tabs you press towards the pedals and the door hinges on three plastic tabs. The little door comes off and you will see the filters side there, just pry it out softly and look at it carefully. also observe the air flow arrows both on the filter as well as the compartment wall.
Checked my Cabriolet yesterday... with 580 miles on the clock, no mold, no dirt to speak of. Looked pretty clean. Ditto for the daughter's Coupe, with ~200 miles on it. No problems on these two.
Cheers,
Jeff