I would offer this advice, but they are all so clever you can't tell them anything. They are a very insular bunch in general and their tie to their land is a bit more than the blood sweat and tears mentioned below, its a bit more like being the Lord of their Manor. I agree with the top post, they would happily be less profitable to save tax. It is intriguing (but not surprising to me) that many UK farmers voted to leave the EU, despite it being their main source of unearned income and the main market for their goods, and despite the National Farmers Union coming out in favor of remaining. I have noticed the young generation of farmers be openly aggressive towards foreign people (not that they actually meet any). It is kind of sad, but when they all lose their farms after Brexit they will still blame the French for it.
Disclosure: worked a lot with farmers, and have some in the family