This is an issue you are better off discussing with your bank and parents also. However, the bank can only advise you.
I am with Lloyds and their planned overdraft scheme works like this:
First 3 years you pay no interest to the sum of money you borrowed, however, after 3 years, if you have not payed the sum of money back, you then have to pay the sum of money you borrowed plus interest which adds on each year.
This planned overdraft can only be used for 3 years on a student account, so if your course is a 4 year course, make sure you've have financial stability for that 4th year, so you don't have to use the overdraft then. Otherwise you will be paying the sum of money you borrowed plus interest, which would lead you into more debt.
After your course has ended, your account then changes automatically to a graduate account. (The bank has these details when you go for a meeting with them).
I cannot stress enough that if you do use want to use the overdraft, have a meeting with the bank first & plan the overdraft. Otherwise, if it's unplanned you pay interest regardless.
& using the overdraft only turns into a bad habit if you use the overdraft for unnecessary things (e.g. Clubbing everyday/drinking/eating expensive meals). These are things which could lead you in further debt.
Make sure you only borrow from the bank what you can realistically pay back, within those 3 years before the interest is added because this will help minimise the debt as you will doge paying the further interest..so budgeting is key, even with an overdraft.