Having an interest free overdraft can be very useful at times but remember banks will only give you an interest free overdraft if they can make their money in the end. The way they do this with students is by adding a large amount of interest once your course has finished. So if you have used up all of you overdraft come the end of your course you will find yourself having to pay interest on it.
My advice is only to use your overdraft when absolutely necessary, certainly do not see it is an additional loan to spend on whatever you feel like.
student finance UK - for students, by students 
