So I cleaned all the door seals with water only and it has definitely made a difference. It has heavily reduced the noise. I didn't clean the felt part though. I might give it all another thorough clean and see if I can completely eradicate it. Thanks for the advice.
Is it worth putting some sort sealing agent on the rubber? Or should I take it back to dealer and get them to apply something? I don't really want to have clean it regularly.
BMW F30 328i | Sport Line | Mineral Grey | Bi-Xenon | Rear View Camera | Extended Bluetooth/USB | Sunroof | High-Gloss Shadow Line | Anthracite headliner | Black leather