After two flood events in the last year and the problem of drying out the carpets I have now found out (I think) why it does it. The drain from the air con under the dash runs out to the engine compartment. It has been stated that cleaning the pipe cures the problem, I did and then it flooded again. The exit which carries the water is open ended and horizontal with a sponge collar around it presumably to stop water ingress. Since this pipe is horizontal it would seem easy for water to run back into the car when pointing up hill. On the inside bulkhead wall there is a drain hopper which is held on to the bulkhead by two clips, I have removed this hopper from the clips and repositioned it so now the whole pipe system is down towards the front, a bit of extra flexi pipe is needed. The condensate draining out is running faster than ever before and the hopper which is the bit that you are supposed to clean with a bit of wire was squeaky clean anyway. Since there appears to be very little on the web about this with a 9 3 I wonder anyone else got the same problem. Of course the water drips in quite slowly probably over a period of weeks or months the first you see of it is when the rear offside RHD footwell is jolly wet. All down to ease of manufacture I suppose but what a pain.