It's not necessarily bad, since it's an interest-free overdraft and you'll probably get a graduate account with an overdraft limit which decreases slowly so you have time to pay it off.
But it would be an idea to try and keep out of your overdraft, simply because you might end up in a situation you didn't expect where you might need the money but can't get to it because you're well into it as it is.
If you need extra money, try and just avoid spending money on clothes. Go to the outlets now before you get to uni and you'll get everything mega cheap. the Levi's outlet in Cheshire Oaks does things like 2 pairs of jeans for £8, and they've lasted me like a year and a half now without even a tear. You can get funky tees for a fiver each and the like; just stock up before you go.
Obviously it's the driving which is going to be the biggest spend here, since lessons will cost you somewhere around the £20 mark for an hour. Shop around for a cheap instructor, but when you get in the car, make sure their license is pink not green, otherwise they're learning instructors, and should be charging you reduced rates imo (that's what my instructor used to do - it's only fair). See how well you can then do without a car and everything. It's good to pass your test when you're young, but if you don't need the car, it might be worth avoiding, since the insurance alone will cost you that overdraft, let alone the car itself, MOT, tax and fuel.