Philip - continue to work hard at those a-levels and get the best grades you can. For many the BBVA loan is the only way to go, hence why the terms of the loan are shocking, if you have the money then great!
Immerse yourself in as many activities as possible, get a part time job, visit your local airfield, attend FTO open days (take what is said at these with a huge pinch of salt), visit the flyer exhibition at Heathrow, and ask to visit the flight deck on flights that you are on. These activities will help to demonstrate your motivation to become a pilot, of which recruiters will want to see evidence. This should also help demonstrate to your family how much you want this job. If you want to do it and get the loan you will need to have them onboard. However I would ask yourself if you feel comfortable with using your parent’s home as security for a loan?
Most importantly before you spend any money, get yourself down to Gatwick for the initial class 1 medical – without this you will never be able to fly commercially.
I think it’s worth bringing yourself up to speed with what’s currently happening in the aviation industry. In the current state of affairs Monarch will most likely not be recruiting cadets for a while. BA on the other hand probably will. Look at airlines and see how they recruit their pilots, what do they look for when hiring new pilots? The low hour market is flooded with people that all have the license, what makes you stand out?