You can do either. I guess they are spray chrysanths are they? What you can do is lift them & get rid of the excess soil, trim the roots back & cut the tops down to about 3" (don't do metric :D ) then "pot" them up in a seed tray in fresh compost & keep them frost free & dryish till about January. Then if you give them a good watering & a bit of bottom heat you can take cuttings from the new growth and pp them into multipurpose compost & pertlite (50:50 mix)again with som bottom heat & they will root in about 2 - 3 weeks. Then you pot them on & plant out after the last frost & throw the old stool away.