Someone may be along who has actually towed with the C4, but I do hope that you realise that whether their experience will be relevant will largely depend on what they towed with the car. Ideally you need someone who has towed your exact model of caravan, and that they have loaded and driven it virtually identically, otherwise the information is potentially flawed, as its not comparing apples with apples.
So please bear that in mind if you get any responses.
What I have found out about the car is it has a maximum braked towed load limit of 1600kg, whilst its unladen weight is 1310 (Figures from Parker's) I must comment that the 1600kg does seem quite large for such a vehicle and it would be worth checking the cars weight plate to confirm the cars legal limits.
Car manufactures have to test the car to find the heaviest trailer the car can repeated start on a 12% gradient. It make no reference to how the trailer will tow at speed. The test trailer is small and virtually ideal where as caravans are large and far from ideal trailers. consequently, the UK caravan industry has guidelines to help caravanners avoid poor matches.
In all cases the cars weight specifications must not be exceeded that is law, but the advice is for Novice caravanners to chose a caravan with an MTPLM not exceeding 85% of the cars kerbweight. As experience grows, the industry guidance suggests choosing caravans with an MTPLM not exceeding 100% of the cars kerbweight. I must stress that applying this advice does not guarantee safe or even good towing.
Assuming Parker's figures are correct, then with a kerbweight of only 1310kg, A novice tower should be looking for a caravan with an MTPLM not exceeding 1113kg and only raising it towards 1310kg as experience is gained.