You seem to be spot on, thanks! Just checked Google images and there are some that are bear a clear resemblance.

Benign or baddy? I don't really like the way it shades out the ground it covers with overlapping leaves and feel if I don't at least contain it then the current diversity of weeds will suffer. This is a wild slope below my garden that's part of an extensive and happily undeveloped area that's scrubbed and wooded over. I removed a lot of Clematis and dead bramble brash in the immediate vicinity and I'm now happy to let volunteers appear. I don't want to preclude a natural plant from it's chosen environment but it's a bit keen. May just bash it back a bit each season.