Don't think they should be moved when still in flower Mr G.
A friend gave me some she had split a few years ago, round about mid-March I think, quite deep rooted they were, she lifted them with soil and roots, divided them and replanted. Mine have done OK. More expert advice to follow from more knowledgable gardeners I expect.
Twixt optimist and pessimist the difference is droll, the optimist sees the doughnut whilst the pessimist sees the hole
They say they don't like being moved at all, but I have never had a problem. I'm with Geoff Hamilton on the "moving stuff around" thing. I do it when I feel like it. Water well, don't lift till you have a new hole ready, puddle in, and shade from the sun, if there is any. Moving on a dull wet day is ideal. Though, having said this, I would be wary of messing about with a large well-established clump that wouldn't lift easily.
Thanks all, Mine a flowering their socks off at the mo. Ive found the plants which get a lot more sun in summer are not doing as well. I want to move them to a more shadier side of the garden ! Regards Mr G