Try changing the battery.
Charge it, replace it,test the alternator,Charge it, replace it,test the alternator,
changing alternator belt on vauxhall corsa
Any alternator will charge at idle.
Check fusable links
battery is low charge. Take it for a long drive, to take the load off the engine from the alternator charging it.
alternator is bad
Changing an alternator isn't GENERALLY a difficult process. I'd estimate around an hour of labor - so whatever they charge per hour plus the cost of the alternator. Possibly a couple a hundred bucks.
A bad belt, a bad regulator in the alternator or bad brushes in the alternator.
poor charge or intermitant charge from the alternator, also check condition of the alternator belt
what is normal price alternator and labor
by changing load its terminal voltage changes.