Hello Andrew
The C5 aircross model has a large number of engine size and power variations. Also I from a quick search I have not been able to find details of its towing capabilities. One thing that I am always wary of when it comes to French cars, is the way they sometimes quote a maximum towed weight allowance that only applies when the car has no luggage or passengers,, not a very practical thing for caravanners .
We really need to know the data from the cars weight plate to establish if the model you are thinking of would be suitable.