Thanks everyone for sharing your thoughts.
I've had a look through the LA planning portal at the permitted development applications that have been submitted recently - quite a difference in the detailed provided.
The landowner isn't interested in selling the plot until he gets a buyer for the much bigger plot next to it. Not sure why he split into two lots, hey ho back to the search.
The plan for the land is a market garden business so need storage, polytunnel etc so need to get an understanding of what the planning officers are supportive of.
On Cornwall Council's planning site, I find it very difficult to filter search results for PD notices as opposed to PP applications !!
Anyway, as to splitting up land for sale [member=202015]Woodland Warrior[/member] : this is very common from my experience when the land area is already fairly small and particularly when there are no buildings or structures. Land agent will have advised the seller on how "best", from their experience, to offer/split the land for sale to potentially gain best sale price. I expect the seller is holding out to keep his/her options open, e.g. a buyer might come along who is only interested in buying the full acreage for sale: if a sale to you for the smaller lot is complete, the seller will have lost that other potential buyer. (Who knows though? It's a bit of a game!)
If you can afford to do so at risk (and you are really happy with the lot for your market garden biz), there's nothing to stop you putting in a planning app' for development of the land even though you do not own the land. I'm not sure what the PP fee is for an agri' land application at the moment, but it wasn't exorbitant five years ago. (Actually, I seem to recall, it was the same fee as an agri' PD notice - don't quote me on that though!)
And I'll bet 'your' LA will have a policy for supporting/encouraging rural businesses: Cornwall Council does, but it didn't like my 1st app' proposal for the siting of my storage facilities and the Parish Council were against my proposals to set up a tree nursery completely !!!!
BUT it was always pretty clear that I would receive planning permission for secure equipment storage facilities, to enable my start-up agri' biz, as long as I jiggled things around wrt to CC planning officer concerns ! And when it came to my revised PP application, there wasn't a murmur from the Parish Council !! (I'm guessing the Parish Council had been advised by CC that my dev' was going to be approved. I really can't say whether that is true, but it seemed like it !)
It cost me a bit more to set up my alternative stores site with excavations etc, but heh !