Hello to everyone.
I've fitted to my Omega a car alarm (Viper 5901) with remote engine start. Although the aircon was fixed previously on Low and the engine was started remotely for about 12 min., no significant cooling resulted. The air coming out from vents was almost not cool at all (ext. temp. 36 deg. Celsius  :). When I started to drive the car, the air coming from vents cooled down fairly fast. The question: is this normal or should I check the cooling agent pressure? (BTW, almost every time I collect the car from the Opel maintenance  workshop,  seems to me that the cooling agent pressure is quite low (would it be interesting for them to "drain" the circuit to collect some cooling agent?!!). My engine is a 2.2 Diesel, 16 valves.

Are fans coming on with aircon?

Yes. So I was wondering whether it is normal that with engine on idle the air is not cooling.

Sounds like there is no aircon cooling at all. Have you checked to see if when it is remote started that the aircon compressor clutch activates? If not then it could be a low refrigerant pressure or something even worse.
I cannot see any dealership removing refrigerant as part of a service either. It is more probable that you have a small leak that causes them to to top up the system as part of a service. Its more likely when it happens every time it goes into them but they should have informed you of there being a possible leak anyway.
You need to ask them face to face what the reason was for the problem after the service they did.
Hope you sort it and 'cool' down soon.  8-)  :y

Well, I didn't check if the aircon clutch is activated on remote start. It might be that the alarm starts the engine but it does not activates the aircon clutch (have to check what is that clutch :)), obviously it exists! ::). Thanks for the answer!