Have the same problem with my 16V, searched through the forum and done the following.
1. Replaced both missing door membranes, with good quality builders plastic and duck tape, my electric window motor both shagged due to these been missing.
2. Removed blower motor and found water incoming to foot well, removed balck leaf guard and resealed with silcone.
3. Unblocked drain channels on "A" pillars with wire coat hanger, blew out with air line and tested by fitting a 3/8 adapter from my garden hose to ensure water was free flowing.
4. Cleaned below scuttle tray, found leak coming from incorrect fitment of grommet for clutch cable, refitted grommet and used silicone on all bulk head grommets.
5. Unblocked scuttle drain on NSF with coat hanger and tested with garden hose.
6. Ordered new scuttle panel as my old one is cracked.
7. Hoovered passenger side footwell with local car wash hoover and hopefully leaks are now repaired
