Hey, i had a similar problem in an older polo, running on the passenger side of the dash, down the side into the area below the passenger door is the hose for the back windscreen wash. The hose has a connection just under the passenger dash, if you pull the carpet you will find the hose, or most probably two ends of a hose! they simply slot back into each other with no clips, and there is the problem. I fixed mine but putting a clip on and lightly tightening it without restricting the pipe, stopped all leaks to date!
If that isnt the problem, the other most likely is a blocked condensate hose from the air conditioner, in which case you should take it to your vw dealer, air conditioners can become little buggers when you try to mend them yourself, but if you are handy with tools and have a haynes then go for it!
Good luck and i hope this helps.
James x
James Rooney
January 2009