I have blogged about Lesser Burdock (Arctium minus ssp. pubens) previously, and Mike Wilcox has also independently come to the same conclusion i.e. it is very common, looks and behaves like a discrete species, and is the dominant species in much of Mid-West Yorkshire.
The other Lesser Burdock, they really do need different common names, (Arctium minus ssp. minus) in comparison is very much a plant of the south and is the dominant form in Huntingdonshire, where the following photo was taken. Note the small flowers, short pedicels, and the rather neat arrangement along the axis of the branch.
So the quest for Wood Burdock is ongoing, but distributional data on the other taxa is rapidly accruing.