As far as I can tell, from both observation and reading, many of the 500 species campanulas are good for bees. This is probably because they propagate quite freely and are already very attractive plants so maybe the plant breeders did not feel the need to muck about with them in order to make more dramatic plants. From the wide variety of campanulas that grow happily in the UK, some are native wildflowers and others are good reliable imports that have become popular garden plants. All of the following are worthy of a place in your garden: For herbacious borders:
Campanula persicifolia - blue or white; tall (50cm) elegant stems with the flowers rising up the stem. So common it has become 'naturalised' in some areas - will seed itself about but not invasive
Campanula glomerata - denser habit, 60cm with large deep blue clumps of flowers at the end of its flowering stems
Campanula lactifolia - great mass of leaves to 1m with a ball of pale pink bell-flowers at the top of the flower stems.
For pots or rockeries
Campanula carpatica - small tidy mounds of foliage with disproportionately large flowers - 25cm
Campanula poscharskyana - small trailing version - trails to 50cm
Campanula rotundifolia - our native 'bellflower' which grows wild in Scotland but does not require acid soil. Its is a smaller plant - 30-40cm and will be quite happy at the front of a border, in a rockery or even a pot but do not overwater.