This is absolutely not a matter of the GOSH staff's competence. This condition is not curable. There is no treatment. To say that the GOSH staff's inability to treat this child shows incompetence is to have no understanding of what that word means. If the kid has appendicitis and the doctors fail to treat it then yes, that's incompetent. That is a condition which is easily treatable. But that is not the case here. The issue is not whether THEY could help, the issue is whether ANYONE could help and it was fairly clear in this case that no-one could.
The American in question (who, by the way, has a financial interest in the treatment he offered) even conceded it would not reverse the extensive brain damage which had already occurred. The treatment has never even been tried on this variation of the condition.
In terms of who makes the decision in the case of a minor who is not able to make their own decision, that should be the parents but there has to be some process if the parents are making decisions which the doctors feel will harm their child. If the kid has appendicitis and the parents want to pray about it and hope it goes away then even as a Charlie Church I'd have to say that should be challenged. If the parents and doctors can't agree then that's where it has to get legal and someone has to arbitrate. What other process can you have? These cases are rare, usually it IS the parents who get to decide in consultation with the doctors. But you have to have some process if the parents and doctors are unable to agree and the doctors feel the parents are making decisions which will harm their child.