To help with keeping Botrytis disease at bay during the cold weather, here are a few things you might find helpful.
(1) If, like me, you show your plants and want to keep them growing through the winter, try to keep the minimum temperature at about 5 degs C.
(2) Watering plants from the bottom helps keep the compost at the top of the pot on the dry side.
(3) When warm enough open windows, doors or both for as long as possible to refresh the air.
(4) Keep plants like Angels, Bi- or Tricolour away from the sides of the greenhouse as these are more prone to botrytis. (I always make sure they are near the aisle side of the bench where it is warmer.)
(5) An electric fan standing on the floor the opposite end to the door, helps move the air around, especially if your benches are slatted like mine.
(6) As I water from, the bottom all the year round, I fill my pots nearly level to the brim with compost. This stops a cold pocket forming at the base of the plant in the hollow you would normally leave to aid watering.
(7) Most importantly space your plants well, so that they are not too crowded and to ensure they get plenty of air flowing around them.
As you can see I water my plants by standing them in 2 litre icecream cartons, I only give them a few minutes in the winter