The child is British if they were born here. Assuming the parents were British.
Until a person is registered, they can not access their rights. So the parents register them.
It doesnt make them property of anyone. The child is also not the parents property.
I assume one of you parents are Spanish? Not everyone can just say 'oh I want to spanish/german/Japanese'.
Your nationality isnt a choice for the majority of people.
Your parents have to make choices on your behalf, these choices should be in the best interests of the child and within the law.
Christenings are not the same as genital mutilation or non registry of birth.
Changing religion or ditching religion is reversible, for a start. Besides you think it's ok for a parent to deprive a child if its rights as a citizen and make that choice for them. Choose that lifestyle, but not religion?
Comparing FGM to a christening is simply awful. And I am not even remotely religious.
Non registry will already cause the child probelms by the time they are an adult.
If you could be bothered to read the thread you would see that the child can not just tip up and register themseleves.
And no one on this thread has suggested it's not legal to educate your child outside of school.