1. Bulkhead drain hole (under the bonnet) blocked by leaves? If so clear them out and run water through the drain hole to flush it - use a watering can.
2. Check your coolant level - your heater matrix might be leaking - the water in the car will have a sweet smell if it is this.
3. Windscreen leak. Check by putting newspaper down near the screen. If it gets soggy you'll know.
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