Seat Ibiza faulty electrics

what started off as a minor issue is starting to show more serious symptoms, firstly about 6 months ago I noticed that the engine would rev slightly higher at tick over to around 1,000 rpm, gradually this has developed into poor starting and occasionally the climate control fan stops working? not sure if they are all related, but I had my battery tested and it was found to be in good condition, could it be anything to do with the alternator?. my local dealership innitally advised me to get the aircon serviced and cam belt changed etc? funny enough these issues seemed to start after it was last serviced. I wouldn't like to have to pay additional costs for unnecessary work if I can help it.