My wife had the same issue. Car constantly damp and misting up. After trying to work out what was going on I found about 4 inches of water in the footwell.
I phoned Drive Vauxhall in Weston Super mare and - as the car was just out of warranty (by days) they said they would 'have a look' for many pounds per hour. I drilled a hole in the footwell, applied rust treatment to prevent corrosion but now have electrical problems from the moisture. The front nearside led indicator doesn't work. I cant find out why. I took off the side mirror - the indicator on the mirror does work, and water flowed out. The electrical connection is hand wrapped with insulation tape on a new car!
I was hesitant in buying a Vauxhall, but it has turned out to be everything I thought it would be - as has the support from the dealer. Cars and dealers that belong in the 1970's.
If anyone at Drive Vauxhall in Weston super Mare reads this please get in touch -
billjeffrey@live.co.uk