I run a 2005 BMW 320 Cd with 48,000 miles. I was recently away for a week's holiday. On my return the air-con is not working. The fans come on but no cold air is emitted. I have had the vacuum and gas levels checked by Kwik Fit, both of which were fine. They indicated that the fault may be a faulty compressor or a relay, but admitted they had no expertise with this type of car. The car is covered by a maintenance package and has just gone out of warranty. BMW has quoted £60 for a diagnostic check and £717 to replace the compressor. Have you any suggestions as to what the fault may be and how I can resolve the issue for a lower cost?