Well, the first skein, which was left in the dyebath for an hour, then hung up to air and dry, turned out a bit pale and patchy :-
The second one I left in overnight :-
Still quite pale, and lighter in places, but not as "blotchy" as the other one.
I should get another harvest of leaves later on so I'll try once more. I'll maybe put the first skein back in again to see if I can get a darker colour.