a) David Archer planning not to bother going to the police over the hay.
Surely it would be easy enough to request the dealer name his source - he has to have a paper trail of how he heard about the hay and what who was paid for it. So if the hay had identical grasses in it as that of their farm, and the dealer can name who it was bought from, eventually they would get to the thieves.
b) Despite every other show on R4 making serious attempts to avoid spoiling the plot by revealing too much, continuity 99.99% of the time tells us what's going to happen in the following episode of the Archers.
c) How so many interviewees start an explanation with "So..." Where there's no need. They could say "The survey / experiment / method / process we use..." but insert this nonsense noise word "So" (mainly science programmes/ interviewees).