Canon B3 (4) is quite clear that the decision as to which form of service is to be used lies with the minister who is to conduct the service. It goes on to provide that where the parties cannot agree the bishop shall decide.
In practice this is a matter of concern to a very small group. The vast majority of those I meet for baptism, wedding or funeral are thoroughly "unchurched" when it comes to liturgy. Talk of the Book of Common Prayer or the Alternative Service Book is gobbledegook to them. What does help is talking about the content of the service for the particular occasion. In that I do not see myself as dealing with "customers" but entering into a pastoral relationship. This starts where they are and seeks to relate the gospel to it and move us on a little further in our journey of faith.
The Rev IAN BLACK