After having several frosts the Dusty Miller is droopy but nevertheless alive. Can I cut them back to the ground to neaten things
Dusty Miller is called a half-hardy perennial. It behaves as perennial in zones 7 or warmer but may suffer winter kill north of that. Like snapdragons, they sometimes come back in the north particularly if winter is mild or snowfall covers them, giving protection from cold winter winds. The dead foliage is part of what is protecting your plants. If you trim it back, you need to substitute a 1-2 inch layer of mulch over the plant crowns.