Investigation.

        It's very prolific - BUT - I'm not too keen on its location, in a crack in the cement - SO - today I had a closer look around it.
        Two things came to light.  I'm not sure if they throw runners, like their bigger relatives or just propagate via seed.
HOWEVER 
        I found out that there is, already, one Pup close by and I might be able to lift/move the parent as well, as it seems to be bigger than a crack it's sitting in.  I also found yet another Buddleja seedling making a sortee into my territory again.  Thou shalt NOT PASS!!