Rizla,
I suggest your problem may be the door seals / sills, or the foam seal joint in the air inlet ducting which has perished, allowing rain and spray water into the air duct and then to the passenger footwell.
On the SE there is a very small lip on the plastic door sill - S2s have a much taller lip. It's to stop the water which runs down the A-pillar seals or B-pillar pouring into the car instead of out under the door. There may also be a couple of cuts in your door seal at the bottom to let the water drain out.
There is a heap of "leak stopping" info in The Service Notes manual Addendum no 1 "Water Ingress; areas of attention" pp 55-73. It's quite comprehensive. Too comprehensive actually - I don't think you need to do it all. About all they missed is adding extra foam seal (or silicon sealant) to the top of the windscreen to prevent water getting in past the header seal and dripping down at the A-pillar. This is a better solution than the "drain tube" method in my opinion, as it treats the cause (water getting past the seal, not the effect (water dripping onto your knees).
The other thing it misses is the foam seal in the air inlet. It's under the wheel arch liner and if it has perished you'll get water soaking the passenger footwell on the move (not at rest).
John
edit: I see Matt types faster than me.