OK if the battery is draining there is an issue TIP, if jump starting or charging only ever use the charging points under the bonnet if you connect at the battery, you can cause damage to other components. You can test for yourself with a multi-meter at the charge points under the bonnet. Engine Off you should measure 12.5 to 12.8v (healthy battery) with the Engine running you should see 14.5v + With the engine off and the Muti-meter set on amps check at the charging points and the alternator for any current flow. Alternators do die but very rarely, more often than not the fault is with the Voltage regulator on the back of the alternator. Remember that Garage work on an hourly rate and it is easier/quicker often to change parts at the Customers expense than actually fix them.
If you are a logical person there is very little you won't be able to fix/improve on your car with the help of a Diagnostic program and some basic tools. Not only will you learn about your car and how it works but you will be in position to decide what jobs you may need the help of a Garage with. There is a tremendous amount of information available
Dave