Hi Ricky. I'm 22, and found myself very much in the same shoes as you are currently when I was at school/college so hopefully I can give you another useful option. I found the whole two years of college to be very pushy towards university, and as it turned out I was in the very small minority that didn't end up going as I just simply wasn't interested in any of the courses being offered.
I chose the 'start at the bottom and work your way up' route, and started applying for any job I could at any airport as soon as I left college. Keen to get started, I took the first thing I was offered, which was a baggage handling job at Gatwick. Not the most convenient for me with a 1 hour and 15 minutes commute to and from work at silly times of the day but it got me on the first rung of the ladder which was what was important. I worked a summer temp contract there and this small amount of experience got me straight in to the same job but with another ground handler at Heathrow which worked a lot better for me (much shorter commute, better pay, permanent contract).
I stayed in this job for around 2 years and gained a whole wealth of knowledge and experience whilst working in a (admittedly fairly easy) job that I enjoyed doing. I put myself forward for every opportunity up for grabs there and ended up doing loading, aircraft pushbacks, de-icing and even brake riding on Boeing 787's! If you are not familiar with this procedure, this is when someone is required to sit in the aircraft's cockpit and operate the brakes/systems/apu while the aircraft is towed between stands - very interesting for someone with an interest in flying. Most importantly, it paid a decent enough wage for a 19-20 year old living at home, topped up as often as I could with any overtime, which enabled me to save and gain my PPL.
Fast forward a little bit, I am now working in the operations department for a business jet charter and management company and have a PPL and more than 100 hours in my logbook. My short term flying goals are to gain the night and IR(R) ratings, whilst longer term is to still get my ATPL and get paid to do what I love. However! Like you I was fully fixated on becoming a pilot, but I have realised it is not the be all and end all. As it stands, I have an enjoyable career to pursue in my current area of work (and interest), which also allows me to get my flying fix, build hours, experience and ratings, whilst also saving for the future. Working in aviation has also given me many contacts and opportunities which wouldn't have been possible if I'd have chosen uni!
Sorry this has turned in to a bit of an essay but the main thing to draw is that motivation can and will get you a long way, and it seems you have bundles. In the short time I've been involved I've learned that experience in aviation is just as valuable if not more so than qualifications, but stick at your a levels and get the best grades you can! The main advice I have for you for the short term is to get out there and get involved with whatever you can (plenty of suggestions in the previous replies); do your best to get a part time job so you can have the odd trial flight here and there - I found flying to be extremely rewarding at the beginning even if it was a 45 minute local flight practicing turns and straight and level flight; draw up a rough plan, where do you want to be and when?; and try and get some work experience at a flying school - I managed to log nearly 3 hours for nothing in my week of work experience just sitting in with instructors ferrying aircraft to/from maintenance! Best of luck to you with whatever route you take and if you have any more questions feel free to send me a private message!
Be motivated but also don't forget to have fun in the mean time, I've lost count the amount of times I've been told "I wish I was your age again"!!!