The alarm problem is most likely down to the battery in the sounder which has degraded and your car needs one of two things - a new sounder (about £60 + fitting + VAT) - or just remove the sounder (detailed elsewhere on other help forums).
To answer David - the binding rear calipers were covered by a dealer callback some years ago, but lease companies never bother doing it, and if your car was previously owned by a lease company, you can bet it won't have been done. The fix is a different caliper which doesn't lock up.
The air-con issue you have is a typical aircon fault - either a hole in the condenser (in front of the radiator), maybe a leaky pipe fitting, or in a T-plate vehicle, as it's getting on, the compressor may be faulty if it's been running without coolant (and therefore oil). Get it checked by a proper aircon engineer, not a dealer who will take your money and keep filling it up, and if they did fix it, charge you the earth for the work compared to a proper aircon engineer.
Rob, August 2008