Newsround Blog agrees with the sentiments of the above letter, but with the following additions:
Funding is not insubstantial, yet the service provided at present by the BBC is skewed, with little or no provision for teenagers and those kids from vulnerable groups. The BBC has been shown to surreptitiously discriminate, especially against older children. There's no point in extra funding for TV if that funding is merely to entrench the status quo.
See also this blog about Phil Redmond's RTS lecture. Phil was not one of the signatories.