Exact same things been happening me, left it into the garage yesterday, alternator needing reconditioned or replaced mate!
The car is actually running on the power you've been getting from your mates car when you've had them connected from jumping it. Not enough power coming from the alternator (11volts mine was reading, should be 14).
What's everyones thoughts on prices? I've been quoted £100 for a recondition and labour.