I have a water leak and the foot well of the front passenger side is always completely soaking. I've had a garage look at it and they cant find anything wrong

They checked the inside of the door where the glass travels up and down and put a hose on the door for an hour. All for the princely sum of £80
I regularly clear the drain tubes under the front windscreen thinking it was them but the carpet is still soaking wet. So its not them I think.
What else can it be? I've just started offroading big time and this is holding me back.
Any help would be very much appreciated.
Thanks
Catweezil