I've got lots of seedlings and cuttings over-wintering in the mini greenhouse. I pop my 3" or 4" pots inside those polystyrene trays which hold small pots of primulas and pansies at this time of year - and are free if you ask nicely - and I'm sure they help to keep young roots nice and warm during the cold months.
G x
aww that sounds kewl. My friend in leicester gave me this fun tip....she puts a tea light in every night into her mini greenhouse and it keep it warm enough to keep the frosts away.