Lift your carpets and check the foamy sponge stuff underneath, it can hold a ridiculous amount of water over a long period of time. Once that stuff gets wet there's no amount of silca bags that will help the problem. Remove if wet and dry out. Then of course you need to find out why it's getting wet in the first place, this can be a complete nightmare.
In the meantime, you can purchase mini sized condensation absorption things in the likes of Homebase. Bung a bit of sticky backed velcro on the underneath to prevent it falling over and stick one under your seat fixed to the carpet. Should help. And I've also heard that for the last mile or so of your journey before parking up, switch the heaters in the car over to cold air and it limits the amount of condensation that may appear. Must be something to do with the difference in temps when left parked.