When I say problem I mean I can force the battery warning light on. If I switch on front and rear heater with demisting the light pops up. Rev just above idle and it goes out. Occasionally it stays on until I switch of an on again. 
 
	All other times the car is fine, charges battery and it holds well enough. Local garage is going to fit a new alternator for £400. The car has been doing this since Oct and hasn't got any worse.
 
	Am I wasting my money? Is the ECU simply doing its job? Anyone else has this on their  x type?
 
	Thanks muchly
 
	Matt H