I have had that problem too. One series of conversations went like this:
Farm house now private dwelling, occupier no idea who owns land.
Went to nearby campsite and discovered location of land owner in nearby village. They warned me owner did not actually farm the land anymore as that was all done by a contractor.
Went to find retired farmer in his very nice barn conversion and obtained address of the contractor.
Visited contractor and got agreement for some hives.
The key to unravelling this chain was the local campsite, i.,e. someone with local knowledge. Could equally have been a local shop or post office etc. Could be more difficult in more remote areas.
Point is land like this will not be advertised so you have to go and seek it out.