In my experience the Class 185s have pretty good aircon year round, in winter it's not too cold and in summer not too hot even when there's not even standing room from Preston to Manchester
It depends where you are in the carriage.
Generally always sit towards the ends of the carriages, and never in first class when it is very hot or cold outside. The Desiro / 185 air con is rubbish in general. There is only HVAC per coach, so if it fails (which they do regularly - passengers may not notice but when you are on the things all day every day you do), there is no back up for that coach. At least with a 170 if one HVAC module fails there is another one, which means that the coach doesn't get completely horrible for being too hot / cold.
The HVAC also only blows out air at the ends of the carriages. So if you want heat or cold air then sit at the ends. Sitting in the middle section you get a load of noise but no air, which can make the middle section especially stuffy in summer. This also means there is no real ventilation in first class so that can get very hot / cold.
The heating only works properly when all 3 engines are on. If there is an engine out then the floor radiators go off, which means on especially cold days you are relying on the roof blowing warm air, which again is fine at the ends but if you are in the middle or in first class you have no heating.
Overall the set up of the system allows for very varied temperatures throughout the carriage.
Oh yes, and there is no way traincrew can alter or reset them, unlike 170s which can be temperature adjusted or reset with ease.