My wife has a 2006 Vauxhall Astra Design Twinport 5-door hatchback. It has become progressively more humid inside over the last two years. I have noticed water on the inside of the LH and RH front door sills that runs inside the cabin, causing dampness after the car has stood parked in the rain. The door seals are undamaged and the door closes and seals OK. I have opened the doors and then run the window down into the door and introduced several litres of water, using a funnel, into the interior of the door. This completely and rapidly drains out from the drain holes in the base of the door. If however, I repeat the experiment with the door now closed, no water drains to the outside and after a while water appears below the door trim on the inside, duplicating, I imagine, what happens in the rain and highlighting the probable cause of the dampness.