Hi there, welcome to the forum
As a site rep, our rules say that, If the last tenant wants the shed he/she has to remove it - if not removed, you don't have to buy it, it just gets left on the plot, complete with anything left inside..
I'd call his bluff and say you don't want it and see what he says, but that may mean he sells it to somebody else. (but they aren't that easy to move
)
On the other hand if he does move it off the plot - could you easily/cheaply replace it, or do you think it may be worth a
small token payment just to keep it there? Difficult decision that one.