neil...........bees are hardier than we think sometimes? i would let them alone and not rotate, they are on the south side for some reason. we can do all the right things and in extremely cold weather it's a crap shoot trying to figure out whether they will survive or not.
if you have feed above them, great, and the best feed IMHO in cold weather is directly above them, on top of the frames. good luck! looking forward to an update on how your bees are doing!