The carpet on my 2.2 hdi did not get wet, the backing on the carpet kept it from coming through, so not that easy to test. Might be a good idea to lift a portion of the passenger footwell carpet just to check.
Hi I bought a 2.2 HDI which developed this problem, took it back to the dealer. They said that the Heater Matrix had gone and it was a common fault. I was lucky and got it done U/G......hope this helps