Lemonade Sal, Emma B put this on another thread; sounds like you might want to read the contract carefully and think about it before getting involved:
"I can't find the details of the contracts for the Britains Got Talent contestants but the contract for those taking part in Cowell's other show, British television's music talent show contested by aspiring pop singers drawn from public auditions The X Factor, has been leaked much to Cowell's embaressment.

As part of the deal, the acts have to agree NEVER to criticise the music boss!

In fact the contract, which runs for 80 pages, also reportedly states that the rules are enforceable anywhere "in the world and solar system" and that artists may not be critical of the company, "including its personnel and, in particular, Simon Cowell".
Breaking this clause imposes quite staggering financial penalties

One finalist is quoted as saying.
"After being kicked off, you're under contract to Cowell's label even if they've no interest in you. Other record labels won't touch you until the deal is over, and then interest may have waned,"

Despite 'heartwarming' articles planted in the press by the programmes publicists that that the winner will receive a £1 million recording contract, this is not guaranteed and the legal document shows that the victor MAY only receive £1 million after at least four albums.

Instead, they will get an advance of £150,000 to pay their expenses for their first CD

In return the winning act makes 15% from single and album sales, along with 7.5% of profits from a tour and 15% of merchandise sales."