Putting my foot down and telling the caravan site owner that we're not prepared to play games or get into some sort of bidding war with a (possibly fictional, although I didn't say that to him) second customer seems to have worked. He's sent another communication saying the owner of both vans is coming down next weekend to finish clearing them out, and we can go to view the two vans on Bank Holiday Monday. He said if we choose to have one, he'll offer the other to the second customer.....yet in his previous communication, he was trying to say that this person had precedence over us.
Whatever, at least things are moving in the right direction now. It's not exactly been the best of starts, but we do really like the site and I guess the site owner is in business after all, so he was probably pushing it a bit to see if we'd bite. Well, I'm not a pushover and I think he knows that now.