Unfotunately this problem is endemic in Audis and VWs.
The drains in the scuttle panel block up with leaves and water backs up, this finds its way into the cabin via the ventilation system inlet/pollen filter.
Symptoms are condensation, wet carpets, alarm/locking problems and brake cylinder corrosion.
If you want to check make sure you press hard on the carpets as there is a lot of foam under them, another option is to run the car through a carwash and check for water dripping into the footwell.
SSE