As you don't say it only happens when rainding I'll tell you why my mat got wet.
I noticed the rear window washer was not working and being due for MOT I thought I'd investigate both the wet carpet/mat and the washer not working. It turned out to be the washer feed pipe going along the roof driver side inside behind the trim on the edge of the roof. After removal of the trim it showed one side had pulled away from the plastic pipe joiner so instead of washer water going to the rear window washer jet it was running down the windscreen pillar behind the trim and dripping on the mat. So if your rear washer is not working that may be why the mat gets soaked.
RAIN ENTRY test, tissue the floor under the dash and up side of driver seat then play a hose with gentle flow over the roof then check if the dash tissues got wet or the driver door side got wet. If dash got wet and door side dry then it could be the drainage is blocked under the plastic grills.
If the door side got wet then it's the door seal or the door slightly distorted.
Rob
Rob, October 2005
