I recently had this with my Scenic.
At first i thought it was the sunroof drain plugs blocked, however after clearing these it was still getting damp.
things got really bad, big puddle under the passenger seat.
I found it to be the heater matrix, to check you will probably see water dripping out on the passenger side bottom of the center console, there is a small removable plastic facia with vents in it. if it is a small leak, wedge a plastic tub under it and leave the engine running with the fans on.
not to difficult to change, i did it in about 20 mins.
aidy
September 2008