I'll be honest, I'm not massively sympathetic, as it seems pretty evident that he was aware of the henges, even if he wasn't aware of their full extent. Also, there is a fair possibility that he was fully aware but "chanced it" anyway, on the basis that he might not get prosecuted or that the consequences would be outweighed by the advantages. That's speculation, obviously.

But nevertheless I think it's possible to distinguish this from the tree, where there was very clearly a deliberate and calculated decision to cut the tree down in spite of the order, in order to make a financial gain.

One other thing I meant to say regarding the amounts imposed, is that a lot will depend on the relevant legislation in each case and whether it sets any guidelines or, more likely, limits on the amount of fine that can be imposed. The henge and tree actions will have been brought under entirely separate pieces of legislation, so it makes a "like for like" comparison even more difficult.