Burger Trailer On Own Land

We have run a burger van for 3 months on our own land the side of a highway it’s doing really well and we love it. We have had food hygiene out and passed with flying colours and have registered our business.

We now have the council come out to us today and they say we need planning permission on our ''move-able trailer" which is towed away to a secure lock up every evening and towed back in the morning.

Is this right or because we don’t pay council for plot as the lay bys do it all boils down to money?? We are very worried for the outcome; we have worked so hard for this!