Are these plants you've grown from cuttings or mature plants you've bought?
If you have a cold greenhouse or cold frame ,I would plant them out in Spring. They may get too soggy in a wet winter. In subsequent years, they will be stronger plants more able to withstand it.
I ordered some dianthus from Hayoft and they have been in the ground for about 6 weeks. All have grown well and three have even had small flowers. They are about 4" x 4" and I'm now wondering whether it would be sensible to dig them up and grow on in pots during the winter. I haven't grown dianthus before so would appreciate some advice as realise they are young plants.
If they're in suitable ground they should be fine where they are Billie. It's wet soggy ground they hate so if they have good drainage there's no need to lift them. If you're worried then put them into pots for this winter and try and improve your soil for next year if you want to keep them in the ground permanently. I love them but we get high rainfall so I mostly grow in pots, but I've grown them in the ground successfully where I've mixed large amounts of grit into the ground first.