Are you talking about campanulas? If so you can move them now, trying to take a good root ball.

What exactly do you mean by white bells? That can refer to lots of plants. If campanulas steragram is correct. In fact most perennials that are dormant now can e moved now.

or are you talking about snowdrops, musiclover? If so, you can move them [and divide them up] when they have finished flowering.

Or perhaps Leucojum vernalis?

Thank you all for your prompt replies