, I am a solicitor with 20 years experience. I will try to help you with this.
The basic position is that he can put it wherever he likes on his own land unless there is some rule preventing him from doing so (eg a restrictive covenant, or a term of a lease). If he is causing damage to your property then he may be responsible harm caused.
Can you give me more details please? Are you suffering any harm as a result of his actions?
he is not causing any damage but his caravanis right next to mypatio fence and directly by my kitchen window if my fence by any chanceblew down onto his caravan would i have to pay
You might have to if the fence was not maintained properly. But if there was exceptional weather that blew down a properly erected and maintained fence then probably not.