Hmmm... I didn't think they were allowed to turn house or farm scale ones down on aesthetics any more, maybe unless it's right on a World Heritage site or something. (There are several farm-scale ones visible in Northumberland National Park from Hadrian's Wall, by the way.)
In fact I thought the presumption had to be to allow unless there was a really good reason not to.
If it's a bit bigger than farm scale I think they still have to have a jolly good reason - like it's on the approach to an airstrip or something. The planners ought to be able to at least point you at something that defines the legitimate reasons for disallowing - the Local Plan or other council document, I would have thought.