Static caravan residential planning lapsed - Public forum - Planning Advisory Service (PAS)

Hello, I'm interested in purchasing some land that's has a residential caravan on site for which according to the estate agent the planning has lapsed. How do I go about reinstating the planning ? Could I do it by applying for a certificate of lawful development. I would be reluctant to reapply for full planning due to cost and chances of refusal. Would it be possible to use the land during the summer for touring caravans with the static van as a wardens residence or would this require change of use. Thanks for any help david