Do you need to appoint a registrar for a naming ceremony? (UK)?

I am looking to hold a naming ceremony for my baby son and we are looking at the non-religious context as we want our child to have the freedom to select his own religion or not if he does not wish to. However, all the venues that I have contacted are asking if I want to appoint a registrar, and if so are asking me to contact the local Council. I just assumed that you had to appoint a registrar - is this not the case? And if not, what is required? Any experience of your naming ceremonies (UK) would be greatly appreciated. Many thanks.