All churches have a formal list of their membership which is called the Electoral Roll. That is, people who complete a form to say that they are baptised, a member of the Church of England and either resident in the parish or worship at the church. People can worship without being on the Roll.
The list is confidential and kept by the Electoral Roll officer, who will approach people through the year to see if they are on the list or sign them up on the simple form. The list is reviewed annually around April for the Church AGM where the new total is announced. The current total (2023) is 165.