2000 Rover 45 loose power and electrics while driving

all i can suggest here is check all the earth points on the vehicle and clean the terminals on the battery and when this happens do you get any management lights come on

Hi, I have a similar problem which has all of sudden started. The difference being the battery is dead, after being fine a few hours earlier, and won't turn the engine over but the car will start off a booster pack. When running there's a noticeable lack of power and if I switch on the headlights when idling, the engine dies as though i've actually cut the ignition. I tried the same thing with the rear demister but that didn't cut the engine. Dashboard lights, oil, engine, battery, ABS, SRS, handbrake are normal if very dim and most of them don't appear when the engine is running. The only one that does is the ABS light, again very dim but with a definite pulsing to it. Multimeter across the battery when running indicates approx. 14.3V. Local garage says, without looking at it, that it's the alternator and wants £200 to replace it. Any ideas?