Many's the time the air con would not go into refrigerate for the first hour to hour n half of the trip and because the pax had all the eyeball vents open the was no air for the drivers. I recall one day holding my cigarette up to the vent and the smoke drifted into the vent!!
In BEA 800s there was a cockpit a/c unit fitted every summer and removed come winter, it fitted in the position where the navigator's seat was (yes - there really was provision for a nav!).
Apparently it made life a lot more bearable but unfortunately when the aircraft were sold on the purchase didn't include the unit. Nor did it include the Decca - still, saved us poor cos' having to lug the Decca box around with us.