If you are in the uk, you are young enough to qualify for free lessons via youth organizations.Google will lead you to them. I don't know if this is the cse in America, but possibly.
For basics, I agree that online 'lessons' can be very helpful, though not a substitute for lessons with a good teacher/coach.
Also, try
http://www.vocalist.org.uk/ for lots of good info on all things Singing . I sing and also do part time vocal coaching for a living and still continue to find great tips at this site.
I hope this is helpful.