Got a vauxhall corsa 05 reg with the same problem.
I found that when you remove the carpet and pour water into the side drains where the windscreen wash is that the water comes straight through into the drivers foot well.
I know this isn't exactly an answer, but it might help identify the problem.
I tried taping up the joins and the nuts where the steering column meets the body. This helped a bit, but the space is very difficult to get into.
M Bilsbrough
July 2009