Hi Rob
I left school and after a few months went straight into flying school. I had a CPLH at 19 and I was flying S61s on the North Sea as Co Pilot when I was 19 and a few months.
Age shouldn't be a barrier in my opinion. I was very lucky and was sponsored so I can't give you much advice on where to go to school. However, there are many threads on here about training abroad and that's where I would start if I were you.
Good luck and there are lots of good guys (and girls) on here who will help you out with information.