Windscreen icing up - Seat Leon

[CitroenC1]

Hi,
My windscreen is icy on the inside on cold mornings, grateful for any advice. Car is Seat Leon 2010. Here is my troubleshooting so far:

• Must be moisture in the car somewhere.
• Checked carpets and boot - all dry.
• The rear seat feels a bit damp - it's hard to tell but it may possibly be damp, certainly not soaking
• Poured a bucket of water over the whole car.
• Windscreen on inside still dry
• Checked door seals - rubber seals all dry, but here's where I am unsure
• The seal on the back doors - seems like a felt material - is wet. Not sure if it should be. Here's a pic - you can't see the moisture but the silver metal underneath is also damp.

Any guidance welcome, thanks