Still talking about Scotland -
Point 1. you used to be able to buy a corner of a field from a farmer and build a house on it - we actually bought such a place in 1988, but it had been built for about 12 years before that. But the planning regulations are prohibitive now and i doubt if it's possible now.
Point 2 - I would have been allowed a static caravan on my land till I received my completion certificate for the house I built, but there was time limit then came into play and it would have had to be removed withing that time - 3 months I think, with possible extensions if it was bought and had to be sold, rather than just rented. So in Scotland anyway I think that information must be wrong.
Perhaps if you say what part of the country you are in others may be able to help you better.