Is there a university air squadron? Is there a gliding club, either affiliated with the student's union or at a nearby airfield? These should help you gain experience without great expense.
If you're going to be working 15hrs a week (the maximum recommended to me), this is going to give you probably one lesson a fortnight if you don't spend any of it on living. The chances are that you will spend some of it on living which means that you would be flying less than fortnightly. At that rate you'd be spending your money on refresher lessons rather than new material. So the way I see it working would be to work through term and fly powered aircraft in the holidays - gliders during term. Should get your PPL after 18-24 months?