Your bees will need less room for winter and that is a fact. Colonies go from 40-60,000 at the height of summer to 10-12,000 in February. It is bad to have too much space in the hive in winter as unoccupied frames will attract wax moth and go mouldy. I try my level best to get every colony into single brood some on 12x14 and some on standard national. You may have to go brood and a half or dummy a hive down, but only you can judge the size of your colonies and they will not all be the same. So, take off honey supers. You may have to feed a couple of kg before treatment if they are short of stores, then treat, then feed in ernest to get 40lb in the brood box. My last inspection is as soon as I can confirm that the queen is laying again after treatment, I have caught a couple of drone layers that way, which enabled me to do a late unite with spare nucs rather than dealing with a drone filled colony in spring. Do bear in mind when feeding, it is not how much you are feeding, but how heavy the hive is. You need to learn to heft. I use the method one member of the forum stated which works for me, lift each side of the hive individually with one finger, then two fingers and then three fingers. When you cannot lift it with three fingers then they have got enough. Others use luggage scales. Get going as you are in the north! Good luck - it is a daunting experience when you first start off.