I have this problem too..Noticed it recently
Water in passenger footwell - no where else.
Have changed the pollen filter housing and filter.
Have sealed the inner pass side door card with silicon.
Thing is - Am fairly sure a puddle appears in the pass. side, when it has not been raining and concerned this may be something more sinister/expensive. Havent used the air con for a while either.
Any ideas guys would be great - thankyou.
Mark