sounds very much like nonesense to me
We have an agric holding.
we errected fencing, have 14 pig arcs, 27 small chicken huts, 1 large straw shelter, and a 60X50 barn.
we did not need planning for any of it, just prior notification for the barn,
do some research on the net, moveable structures do not need planning, unless they are polytunnels,
the only other thing could be something to do with the near housing, however i know farmers who have estates near them and as far as i am aware same rules apply. Local councils have different interpritations of the rules. If you have a good agricultural agent near they will be able to advise. We used brown and co, not sure if they are in your area.