Not sure if you'll have this info but after looking at the table its distinctly possible that the four that came down last season could well go straight back up. Do you have anything that could confirm or deny this?

Incidentally, I lays the lie that the level of football between div's 3 & 4 is similar.

anyone who can remember the standard of opposition in our last half dozen home games last season, would struggle to name any teams at all in this League who could compare to them.

I did some quick investigations before this season started. If I remember rightly, on average ONE of the four relegated teams has gone straight back up whether through auto or the POs.
The season isn't finished yet but it's certainly looking like at least two from four this time round. Certainly all last season's crop are in with a very real chance.