Maybe you saw the foxglove known as Digitalis purpurea 'Campanulata' which produces large bell flowers at the top of the stalk. Pretty sure Digitalis/Campanula hybridisation is genetically highly unlikley, despite what it says at the link. (To the nursery which holds the UK national collection of Digitalis. Scroll down the list.)

Here is a link that might be useful: Digitalis purpurea 'Campanulata'

although there is a digitalis/isoplexus hybrid out - not that I am going for it though.

Well, from what I understand, it IS possible to cross two totally different genera as long as they are in the same family. Think it is called bi-generic or intergeneric hybrids. X Fatshedera and X Solidaster are good examples.

Digitalis and Campanula are not even in the same family, so I don't think such a cross is likely. Sometimes you will see a species (or even cultivar) name that is the same or very similar to the name of a genus, like Inula helenium. It's not a cross between the two genera, but the species name "helenium" is used as a sort of description. I've seen the species name "campanulata" or "campanuloides" before, presumably indicating that the plant has bell-like flowers or other qualities associated with a Campanula. Maybe something got misconstrued somewhere along the way with regards to this Digitalis x Campanula??? I dunno, just guessing here, lol ;-)

From what I have read, the Digitalis x Isoplexis hybrid (the result a cultivar called 'Illumination') actually provoked botanists to reclassify Isoplexis canariensis AS a Digitalis. The story behind it is pretty interesting: Here at Graham Rice's Blog
CMK