Probably the changes in the farming demographic, as the old 'gentleman farmers ' die, the younger, save the planet sustainable organic folk are slowly taking over the family businesses or buying vacant properties. They are more likely to be greens, or at a pinch lib dems. It's still a business predominantly controlled by older men but things are changing down on the farm. The other, and diametrically opposite change is the development of farming as a more industrialised process, super farms, with shed raised cattle, effectively milk factories, crop production over much bigger fields aimed at producing efficiencies of scale with much lower manpower. So a smaller number of people controlling wider areas so fewer voters. The countryside is changing and with it the voting patterns.