Thanks for the quick replies.
I'll try to describe in more detail, hope this doesn't confuse the issue.
There is a step of approximately 200mm from the kitchen floor down to the outside level. The French doors have been installed on top of the step, with the outer face of the door almost flush with the front face of the step (approx 5mm lip of concrete step protruding from under the door frame).
When building up the door opening to take the doors, I installed a vertical DPM between the outer leaf and the block returning to the inner leaf. A DPM was also installed above the lintel. Following installation of the doors, I filled the minor gaps around the sides and bottom of the frame with expanding foam (very messy stuff). Under the door frame I only filled with concrete. I understand that this is the problem and the reason for water entering. It is a very easy job to remove the concrete under the door frame (this is not supporting the doors), I really need advice on what product (if any) I can install to prevent this re-occuring.
Thanks.