Yea just stick to those saturday mornings and weekday evening, you have more than enough. Just make sure you have some hobbies and out of school achievments, its incredibly important that you let the know you will be able to let your hair down and enjoy yourself too. Bristol were very keen to make sure that I knew how to let my hair down, and liverpool did ask about work/downtime management. It also reflects well on your academic achievments, I would go as far as to suggest someone with ABB who has a list of sporting achievments and DofE would be equal or better chances than someone with AAA, perhaps even ABB.