My OH has Periodic Limb Movement Disorder (yes it's an actual thing!) He takes drugs to damp down the movement but my nights are still far from peaceful. We have a 5' bed (room too small to take a bigger one) with 2x2'6 zip & link pocket sprung mattresses. Zipped from the base rather than the top if that makes sense so there's an actual small gap between them. This has helped a lot, but we too are thinking of separate duvets as one of his little tricks is to pull it when fast asleep, it pulls across my face & wakes me up, assuming I'm not still lying there awake & wanting to kill him. We've also made the guest room very comfortable & spent a decent amount on the bed in there, so if all else fails I slope off there for a couple of nights till I feel human again.