So I asked them again various questions, to determine their authenticity. The response was vague and some answers were different to their booking, ie 1 person or 2 going. They thought my caravan was a house, which it clearly from the profile picture is not. They asked me to explain stuff about my "house" which again was evasive, I had asked them about the purpose of their stay, it was like I had irritated them. They also ignored some of my questions, so I declined.
The process to decline isn't great if I am honest, as far as AirB&B is concerned, as it advises your response will go direct to the potential guest. You can't exactly say I don't trust you can you, so I had to word it differently but I think the owner should be able to refuse a booking and not really give any reasons. Seems excessive. Anyway its all sorted and they are not coming, I thank the Community for all their support and advice.