Hiya Sarah,
I have had power steering failure last month, on my way to work pulled up to traffic lights waited like you do, went to go and my power steering had stopped!!
I had no warning lights, that was the first thing i looked for. As far as i know the battery shouldn't have anything to do with it as i drove my mini back home.
lucky i had taken extra warranty out because the power steering pump is around £370 on its own plus labour etc. The power steering pumps on minis arent like every other car, they are electric so if the go they go.
Am afraid to say that power steering pumps and flywheels are very common on minis.
Hope this helps alittle
Sami x
