I refer you to signs saying "NO HOBBY CARAVANS"

Thankfully today people would be prosecuted if they displayed a sign saying "NO TRAVELLERS" although given that the CPS choose not to prosecute in the case cited by Jim that is not guarenteed.

Simply saying "NO HOBBY CARAVANS" is sufficient to deter travellers from trying to use a site but stays within the law.

Same meaning just different wording.