Mulliner Park Ward - where delivered from?

[GTBob]

In the Sixties, if someone ordered a RR with a Mulliner Park Ward body, how would they have ordered it? And where would they have collected it from?
I am curious because the RR used in the film BLOW-UP, reg EVN734C was originally registered in Yorkshire and was originally ordered by Jimmy Saville who probably sold it on before taking delivery.
Thanks
Bob