I hope someone can give me any info on this problem.

Almost after every rain when I open either front door (left takes more water, I think) a lot of water starts leaking from the drain holes on the bottom of the door. I think that is what caused one of the cables of the regulator to corrode and broke.

Any info would be highly appreciated.

Better out than in! Isn't that what drain holes are for? Mine does it if its been parked "funny". Although your use of the word "lots" may mean yo are getting someone elses share too. Perhaps the bottom glass seals are faulty - too short?

Several on here have had corroded door wiring, a shot of wd40? And while you're in there, an extra bit of polythene deflecting water off the electrics?

Perfectly normal imo, more problems are caused when / if the holes become blocked and the rain water can't escape.

Shouldn't all the electrics be protected by the plastic sheet? N.B. I've never had a Skoda door panel off and am just speaking from experience of other cars with regards to the plastic sheet.

My 1U had plastic sheet. Not had occasion to touch the "new" one, so look forward to drilling, like being back at work.