See attached, Not the best pic unfortunately but I will take some more when I get home tonight. There are 2 engineering bricks between the ground level and the bottom of the door.
Thanks for the responses, the chimney breast currently has a gap in it for a vent/ air brick. you can feel the air flow under the floor so I don't think it is due to lack of ventilation.
Yes there is a solid kitchen floor to the left of the patio door.
No pics of the outside but I will take...
I have taken up some plastic flooring and have found some patches of damp on the suspended timber floor. See pics.
Its looks to me like the damp is getting in near the patio door and 'wicking' down the timber to the middle of the room?
Looking under the floor where I can the joists are dry...