Leave them in the ground-they are hardy in the UK
Phlox ,day lilies,all reliable down here-you are spoilt for choice on perennials-others will have some suggestions
I also have a large border that is open to the elements and also on a hill, I have hebe's, foxgloves, hollyhocks, lupins, poppies, cornflowers , echinacea, correopsis, ornamental grasses and verbascum.
Shasta Daisies, white doubles not the tall growing singles ,flower for a long time and are easily propagated so you can increase your stock!
That's one that lots of people have and if you know someone who has any, your on your way!
I have just purchased, the new yellow one which are much dwarfer than the whites, they are Banana Cream, Broadway Lights and Goldrush, I already have taken a few rooted offsets of each, as they each had a few roots on they should hopefully grow!
The fancy name for them is Leucanthemum!