Bad smell from air vents

[rline1983]

Hi there, first post from me on here. Hope someone can help.

I bought my first VW Passat 1 month ago (2009 R-Line) and am very pleased with it apart from the horrible smell I get when I turn on the internal air fan. All the research I have done online tells me its mould building up on the evaporator due to a blocked drain line. I was wondering where exactly this drain line is and how do I get at it (I had the glovebox out and can't see any sign of it in that area or in passenger foot well below carpet)? Are there any other things I should be checking?

Thanks