If its possible (like you said above) to get the carpet out, its so much easier, because most Ford carpet has a tough backing, so you can go at it quite hard with the cleaning solutions, without fear of saturating the sound proofing underneath it.

In the past i have pressure washed a S2 carpet (after a healthy scrubbing of Autosmart Brisk) with no ill effects, just make sure you have somewhere to hang it to dry properly.

It also gives you the chance to clean the floorpans out and check for rot etc etc etc.