Astra getting steamy - too much moisture?

Our recently bought (second-hand) Astra seems to suffer from excessive moisture and steams up in wet weather. It seems to be due to personal moisture from the driver and passengers not circulating out of the car. Using the heater/rear window demister clears some of the moisture but I have never had a car that suffers so badly.
Does anyone know what could be causing this?
We would return it to the dealer, but we have discovered he is an incompetent, dishonest cowboy, and unfortunately we cannot afford to take him to court.
Thanks for any help - a hot and steamy Amanda.

i think all astra MK4's does this...i have a astra coupe and i have to use the AC to get rid of it and have heard of other owners complaining of it

Many thanks for this info. I'll just have to grin and bear it I spose.

i had the same problem with my mk3 astra and i changed the pollon filter and that sorted the problem

hope that helps

Thanks, I'll try that - could well be the problem.

I had the same problem with a 1994 Opel in winter. Found that there was water in the front passenger footwell (under the carpet).

I traced this to a leaky seal around the front wind screen and between the metal car body.

As mentioned another possible cause is the pollen filter (not fitted on my vehicle).

Further possibilties include the drain (into the engine bay) from the cabin fan intakes becoming plugged with debris - mostly leaves and dust that retain water and start to rot...

The passenger cabin radiator (heater) may have a leak.