The look like Leucanthemum - there is a dwarf variety called Dwarf Snow Lady, but yours might be that or the taller one and are only short because they're in a trough, hard to say. And yes, they can be divided, in autumn.

The campanula looks like C. persicifola...

Hi I can see how you think they're in a trough but they're in the ground the fence is actually 3ft and the blooms are starting to fall over as I didnt stake them before the heavy rain they are the same height 3ft but thanks for telling me I can split them

Well, three feet, good lord - I'd estimate, from the photo, they're about 18 inches! Hard to tell scale I suppose

I have an old variety of leucanthemum that gets to about 3 ft too. yes I forget to stake them too. but yes divide in the autumn or in spring before new growth starts.

Mine used to get over 3 feet, its just the ones in the picture don't give the impression of being very tall.