cavortingcheetah,
I don't think you'll find much in the way of getting grants and subsidies for doing nothing. Have a look through the various LMO's Its bloody hard work. It is a tranquil lifestyle for the gentleman farmer, ie someone who started out in life with pots of cash. For everyone else, its a good lifestyle but not necessarily tranquil or profitable.
True you can build on it IF you get planning permissions, however it is liable to CGT
Your last para is more about agents talking the job up. There is a lot of guys who bought these defunct farms and now regret it.