The maximum current that can be drawn is dependent on the rating of the campsite's hook up post and the rating of your caravan's 230V circuit breaker(s).
In the UK the majority of campsites make 16 Amps available at their posts, but outside of the UK it can be as low as 4 Amps.
If your van is fitted with the BIP consumer/fuse unit, its main circuit breaker is rated at 16A, and all 230V sockets and consumers are connected to this one breaker.
Of course, the maximum current that can be drawn from each 3-pin socket will be the same as at home - 13 Amps.