Depends on the council, some don't even come out to look, here in south cambs they will approve part Q on anything, demolish the pole barn and start again no problemYou would need a structural engineers report to state that the building wouldn't need any major structural alterations to facilitate the conversion.
If you have a building that needs some tlc then getting a structural engineer to advise of the 'repairs' that could aid a conversion in the future would be a good investment.