Go on google earth see if you can get dated photos of buildings containers in place more than 4 years ago
or if you have dated photos yourself
If no enforcement action has taken place within 4 years ,buildings become exempt from enforcement action.
If they have been there longer inform council get witness statements and sit tight.
A few years ago i was about to purchase a 19 acre site with intention of starting a garden centre council
told me same, noway would it get planning green belt i pulled out of purchase.
They immediately stepped in and purchased it
Then built a crematorium on the site
Read below click attachment