I recently took my car to get the aircon charged as it didn't work when I bought it- I worked at Kwik Fit many years ago so still know some of the guys there. He put it on the machine and started to run through the process. First is a vaccuum check, which it failed miserably, but after a little investigation we found the bolt that holds the 2 pipes just behind the rad on the left was slack. Took off the pipes, replaced the 2 o rings and reassembled. (Kwik fit now carry all the equipment to repair aircon leaks, and can even repair leaky pipes and hoses) After this the vaccuum held and passes, gassed up and now works perfectly, although its hard to tell how cold it is as its so cold outside. Not sure with the alfa what the minimum temp it works down to? usually 3 or 4 degrees.
Anyone in Fife with aircon issues, pop in to Kwik Fit Glenrothes and see Ricky or Baz!