Hi [member=202014]London Farmer[/member] & welcome to the forum.
Please do not take this the wrong way, but why are you (as are so many other new members to TAS) so focused on being able to build a new dwelling on your land. It's not easy to gain such planning permission as you almost certainly appreciate already: depending on where you buy land, it could be almost as cost effective to buy a house in the nearby village as to build one! I know that might not be quite the same as being woken up by your cockerels or the hungry honking of your pigs each morning, but ....
My thought is that prospective small-holders, who cannot afford to buy the complete thing (home with land), should, to start with, be focusing on buying/renting land in a location that offers opportunity to buy/rent a dwelling in a very nearby village etc. If the rural enterprise is successful and REALLY requires it, then maybe - repeat, maybe - consider sticking more "bricks & mortar" in the open country-side eventually.
[And I should mention that I also like the 'idea' of building a new micro-home on my own land and believe that planning rules are generally missing the point when it comes to self-sufficient or (preferably) profitable rural enterprises; however, I won't be seeking to do so. Part of the reason I plonked for my own holding of agri' land is that it is within reasonable walking distance of several hamlets and a decent sized village for when I eventually choose to sell my present dwelling and buy a house closer to my land.]