The driving theory content doesn't actually take that long to learn (especially compared to GCSEs!). If you download the app and work your way through everything, I think you could quite comfortably take 3 weeks of doing it for maybe 30mins per day before doing the exam. So you can book it for just a few weeks after your last exam ends. Driving lessons - try to book as far in advance as possible. Instructors may only have availability in a few months time, so if you phone up now and get onto their list, it will help!