Where have they been up til now and how big are they? Hellebores are very hardy plants but if they've never been outside it will come as a bit of a shock
They'll be fine if they've been outside in the garden centre. They sound nice plants. Are they in flower?
I've started planting in the garden, just snowdrops and tete a tete daffs in the green. So glorious to get out and start a new year's gardening! lots of things have started in growth and when I pruned the hydrangeas (i always cut them right back) there were already fat buds that I felt sad to cut off. I'd obviously left it too late and gave them a setback. It is quite mild here in Wales, but I'd be quite happy to plant hellebores now. They are great garden plants - I love them. All I ever do to them is cut off the tattered old leaves so that the new flowers can be seen.