my partner's family has owned our property for 500+ years,Wow.... that is phenomenal........not many of us can say that

but I guess that means you are not in a built up area.
Have you or any family members posed as buyers to go and have a look around the premises? That way you can see what is going on, log it down, take photo's and know for sure.
The only thing I can suggest is that if you hear dog fighting and fear or better still
know, that the dogs are being mistreated and not well kept, the RSPCA are the ones to contact, (if the visiting vet has not noticed anything, it may be because the requirements are being met, dogs do occasionally have disagreements when hierarchies' are challenged, it may not be any cruelty going on or being left to fight) 80ish dogs to me says puppy farmer, but who knows?
Councils are all different and you are probably right that they like their fee and that is it.
If you know the dogs are mistreated please call the RSPCA......... people,
unfortunately are allowed to dog breed as a business, if they are paying their licensing fee.
Really, you should have been informed, but if your council are not interested......I guess you can only go down the welfare route now.