Little white plastic bottle of Ant Rid it may be called??, from the big green shed.
Find where they are comming in or few drops among em.
They will take it back to nest and problem fixed.
Always carry a small bottle in the Caravan as will Always have a visit by these little pests in some van Park or other and soon as I see their entry I squeeze a few drops among them and leave there.
Next day they are all gone!!. Works a treat.