Adam,
Firstly welcome to the fraternity of pilots. At 17 years old you have plenty of time to achieve your goal. I had a similar desire at your age.
One piece of advice that I would give you is keep an open mind with regard to your training. I did not train at oxford because I was a poor bugger
, and I am sure the training is good, but you can achieve the same goal at many other flight training organisations. Shop around, and make sure you choose a school that is right for YOU.
All the best with it mate, it is a great job and certainly beats working for a living.
Cheers.