Some posters have suggested that you try to take the p??s and try to avoid the rules, don't do that, instead of a friendly planning officer you will get a really miserable enforcement officer, play it straight.
In England it would be a Certificate of lawfull use, present your application as best you can, when they accept it as a valid application it will be advertised to neighbours, local parish councils, environment agency, highways and probably other. They will all have a limited time to make comments, you can read these comments either online or at the council offices before the application is determined, if you have a lot of adverse comment, ask to put the decision back a month and provide extra evidence to counter the comment. So far it would have cost you very little, if you get refused and appeal it will cost a great deal.