Well, you can put your videos up on YouTube and hope that some record company would spot you. But this thing about reality shows, it really isn't as bad as it seems. Depending on how old you are, a lot of stars are produced from X Factor but you'd probably have to be really good in order to get far.
The standards are less on Britain's Got Talent as there is no age limit, but if you are younger than 16 then BGT is for you. If you watch videos, you'll see that great singers have come from this show. It is a lot easier to win/reach the final than X Factor. They are already doing applications for the next series, which starts in April.
But as Rob says, you should get vocal training or experience if you want to progress.