Kate,
I think you will find the vast majority beg borrow or steal the money:the other options are
1/Military flying - obviously not a route to commercial on its own as you may get killed on the way.
2/airline sponsorship:Not sure what is running at present,but the odds are slim ( i believe BA had 10,000 applicants for 100 places some years ago)
However for both these you still need A levels, so i would look at doing some,
regards