We went into last winter with 4 colonies, 2 vertical (a WBC and a National), plus the two top bar hives (one home-made, t'other bought), and unfortunately lost one of the TBH colonies during cold weather (they appeared to have starved just 2 frames away from plenty of food, and we have to ask ourselves if this would have happened in a vertical as moving sideways in a wider hive might well lead to trouble if the bees are caught in a cold snap too far from food).
So, down to 2. Slow re-queening of the other Drone-laying colony eventually worked - bad weather preventing new hatched Queen from mating for 2 weeks but eventually she was laying and our last TBH is ending the year strong, albeit not with strong stores as they are eating it as fast as they can gather it with having to spend so many days not flying.
And as for our WBC - our first colony: the bad weather late spring led to Nosema. FFS!! We increased ventilation of hive and treated with Nozevit - VERY SUCCESSFULLY. No sign of diseased bees / dysentry since treatment early summer. We will, of course, re-treat winter food supplies.
On another good note, we may be taking on a colony of Black Bees next year, so watch this space!