What I tend to do with plants that require frost protection in the winter is;
At planting out time I pot up the surviving plants which have over-wintered in 3"-4" pots as described above into 5"-6" pots then sink the pot into the location I want them in the garden, then at the end of the season or as the first signs of frost is upon me, I fetch the potted plants into a cool greenhouse to prepare for winter storage!
If some of them are still in flower I just let them flower on in the greenhouse providing I don't need the space with a view to preparing them as I described above when I feel ready to do so!
Should I use some kind of protection to improve their chance of survival?
I would not chance leaving them out doors because; if the frosts don't get at them the cold & damp might!
You could lift them with a good root ball on them, and pot them up in a pot/s of a size suited to the root ball then like me you could place them in a cool greenhouse or on a window sill until you want to prepare them for winter storage.
Then again as you only have half a dozen you could forget about the potting down & haircuts and just let them tick over on the window sill till planting out time. In this way you could have full sized plants to plant out. OK you might want to do a bit of shallow pruning to tidy them up prior to planting out
No biggie if they don't as they are cheap to replace
I grow new plants from seed every year and only save plants from the previous season that have characteristics I like! e.g. perhapa particular coular or leaf markings!