Since last week I noticed that my seat belt feels a bit damp when I use them during the day. Early morning they seem fine and dry. Only noticed on days the sun was out but never had this before (had the car since November last year). Anyone recognise this? 

Water in the bottom of the B pillar - when the sun is shining, water starts to evaporate, and it condenses on the seat belt?

 

Is there a blocked drain in the sill, or a dislodged sunroof drain tube?

Thanks Clockworks, that would make sense. No sunroof but I will check the drain in the sill.