I am trying to set up something that will look like a multiple screen process of setting up a booking for example.
Using session scoped not best way when using Spring Webflow. If you want to share objects between the screens/flows use conversation scope. Use flow scope if you need to share the object between the screens in the same flow.
SWF scopes are in a way specialised form of session and request scopes defined in http session.
Anything needed across the application should be stored in http session object