Air cond probs in new Fiesta

[Sweatbox]

Got new LX Fiesta on the last day of ’09. On 7 Jan the air con stopped working. Took it to dealer on 13 Jan. When I collected it they said it “seemed a bit low on gas”. A/c worked again (still not very cool tho) until the following Thursday when the a/c stopped a second time. Great thing to happen in 38-degree weather. Booked it in for the following Wednesday and also for its 3000k service. Needed new thermo fan, they said. Last Wednesday one was put in. A/c worked again. Drove 300ks to Sydney yesterday, no probs. Started to drive home, drove about ten 10ks and, you guessed it, no air. Anyone else encountered a similar problem. This is the 5th car I’ve owned and I’ve never had a problem with the a/c in any previous vehicle. Each time the a/c konks out after being "fixed" the outside temp is always about 34 degrees, and always after starting the car and resuming a trip after the a/c has been running ok previously. How many times do I have to take the car back to Ford before I need to escalate this, and to whom? I am getting mightily frustrated.
Thanks. (Sorry if this is a bit long and whingey for a 1st post.)