Thanks for posting a photo. That is the one that is blooming in my holding bed. Started from traded seed but didn't know which campanula I had. First year blooming.

Campanula takesimana (Korean bellflower): tamer here than Campanula punctata (spotted bellflower). Still, here, I'd go with C. trachelium (nettle-leafed bellflower: which does seed around a bit) to avoid the running.

Campanula punctata is extremely difficult to pull out (fleshy root extensions). C. takesimana is easier. In my experience here, with C. trachelium, it's easier still.

Mmmm - I love the nettle leaved bellflower and am planning something of a campanula spree next year - given the success of lactiflora, trachelium, patens and latiloba in my wood. In fact, I am chancing my arm with rapunculoides... as well as sarmatica. I also have a white similar to yours Dave - ochraleuca? and also burghaltii. and a downward facing sibirica - hohenackerii?

Also...for sheer unspellableness(?) I have ordered c.kirpicznikloevii and c.takshtadzharnii from Plantword seeds

Very nice 'dave'.

(Anyone have experience with "Pink Octopus"?)

I have a pinkish/purplish variety & I love it. I agree it does spread and yes, it is easy to pull out of areas that you don't want it in. What I would add is that I use it in between plants in new perennial beds - helps the bed look so nice and lush, while waiting for new perennial plants to grow up and fill out. Another added benefit is that the foliage of the bellflowers does a great job of crowding out potential weeds.