Hi bumble and Welcome to garden.org. If you can stand to wait, now (hot weather) is really not the time to be transplanting anything if you want it to survive. Fall after the tops are dying back, or spring before they come into new growth would be the best time. In the meantime, I would give them minimal water to keep them alive, and no fertilizer so they won't increase too much during the summer. Then when the tops have died back you can get at the clumps with a good, sharp shovel and a digging fork. Cut large pieces with a good root ball to move and spread them around.
May we please ask where you are? You can complete your profile (upper left in the blue sidebar, the little person icon) so that your city/state/country will come up in all your posts. It will help a lot with future questions.
