My Fiesta is suffering from water penetration in the spare wheel well - is there a way to fix this?

I have a 2009 1.4 Fiesta Edge automatic which has covered just 6400 miles and is affected by water penetration that collects in the spare wheel well. This only occurs when the car is running on wet roads. I have used a pressure hose but cannot replicate the problem to fix it. Have you any suggestions? If I cannot resolve the problem I will have to change the car.
The water might be coming in via the cabin extractor vents. These are usually located behind the sides of the rear bumper valence and should be one-way flaps to evacuate stale air from the cabin. But if one or both have been damaged, they will admit water thrown up by under force by the wheels when driving in wet conditions.
Answered by Honest John on

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