Hey all,
I had this problem with my 1999 clio. I found the problem was actual the sunroof!
When you take the sun roof glass panel out of the roof, you will see that there is a gutter either side, these lead down into a tube that exits the rain water under the bottom of the car (toward the front of the car).
Where the tubes connect to these gutters I was getting some water in the roof of the car.
When I found the floor was soaking I thought that one of the floor bungs was gone,(no were else was wet) but I managed to take the carpet out and find that, where the pipe connects to the gutter, it was leaking making water tickle down to Pillars either side of the window screen, down there under the dash and onto the carpet under the peddles.
Worth looking at, I suppose the mk3 might have the same set up.