Just to add to this thread. My GF's Mini Cooper brokedown this week with exactly the same symptoms. Whilst driving the clock display went, then the battery light flicked on, then the power steering went all in the space of 5 mins. She managed to pull into a layby and the AA recovered the car to our local garage after diagnosing the alternator had seized.
Apparently to save electrics, when a battery is not providing enough charge various electircal components will be shutdown as and when required. So the alternator wasn't charging the battery and it evetually died.
BMW wanted £390+ VAT for a new alternator then labour. There are two types of alternator available and until they can identifiy which one you need it could be more
So our independant garage fitted a new Bosch one for £170 plus labour.
Still not impressed that a car that is 5 years old and only 40k miles on it needs a new alternator.
