As I said, so long as it's within 12 months, it can be changed easily.
A baptism and christening is exactly the same thing.
THe points above, simply mean that it makes it even easier, if your child was baptised using a different name than that of the given name on the birth certificate. All it is doing is respecting the religious ceremony, which I was referring too.
AGain, I stress, a Baptism is a religious ceremony and between you and God. It is a ceremony within which you make promises on your childs behalf, to God, until such time as they can make them themselves through Confirmation.
threeinabed- all you have highlighted is that the law regarding naming, takes into account and respects this religious service, IF at the time of Baptism you use a different name than that which you registered your child with at birth. It doesn't make my point incorrect at all. It clearly states there that if the names used were different* from registering and baptism, or even, that you all just called your child a different name. i.e. They are registered as Lucy and you all called her Barbara for the first year of her life...
The OP has done the opposite. She has registered a name and had a baptism with the same name.
I'm pleased, reading this, that something which is a religious service is acknowledged by law and can be used to back up further wishes for your childs name.