Dingbatt: The Mondeo I used to own had this exact same problem. When the windscreen was replaced the drain holes that allowed water to drain from the windscreen were blocked. The water overflowed into the airbox that contained pollen filter that in turn led to the airconditioning duct and fan assembly behind the glove box. From there just a short journey the front footwell carpet. Once the water could drain away the problem went away but not long after that the fan started making a noise due to the bearings rusting. Resulted in a replacement fan being required.
I also had a 2006 Mondeo that suddenly developed a wet carpet problem on the floor of the back seat area. It turns out that leaves and general detritus (including silver birch seeds) had got past the rubber seal at the base of the side window and into the cavity of the door. This stuff then blocked the drain holes at the base of the door, causing rainwater to overflow inside the door cavity behind the interior door cards, and from there it flowed straight down to the floor area. In this case, the tight rubber door seals that normally stop water getting in actually stopped it getting out during the gravity fed journey from the door to the floor. A renewed side window seal solved the problem.