I believe I may have looked at the same site near Lampeter (or at least a very similar story). I approached the council and they confirmed the dwelling to be derelict and abandoned (I don't disagree) and I provided the paperwork from the council to the agent. They still marketed it as "with residential potential" for a year after despite having proof there was no potential.Part of my smallholding was derelict and classed as uninhabitable, the other had no roof.
I spent nearly two years battling the local planners to renovate the derelict part and get a roof on the other. With a specialist Co behind me and with four sets of different plans we slogged on.
I went round the exterior of the derelict to make it watertight and started to repair the steading until a STOP notice arrived in the post. I was serious and so were the planners so we continued to butt heads.
Eventually I sent in the original drawings and two weeks later I received a rubber stamp accepting the proposals with the proviso that I treated the buildings as if they were ‘listed’
I saw several plots when I was looking around Lampeter and gleaned some stories as to why they were as they were. I even put a bid in on one derelict but the vendor wasn’t really serious in selling unless one was a cousin.
In 35 years since I was looking the planners are now very aware of the dodges folk try so I doubt you’d get much joy out of your quest.
SS