Sod's Law! I only noticed this thread this morning and…
Last week, I collected my car from the dealer after servicing and noticed a single bead of water, internal, at the top of the windscreen on the driver's side. As the head lining was not wet, I presumed it had come from a wet cloth or whatever during the after-service valeting. I hadn't noticed any more evidence of water since but today I noticed a small stream of water running down inside the windscreen when I pulled up at home after being out, despite it not raining since the previous night. Presumably this water has been trapped somewhere and percolated through after a period of time. A bit puzzling though!
The water I noticed at the garage must have been from them washing the car. I have never seen water on the screen like this before, whenever I have washed the car even with a power hose or when driving out in the rain.
I shall visit the dealer on Monday to discuss and hopefully resolve the problem under warranty, before any water damage ensues,.