Hi vistasp,
Thankyou for your response. That thread was helpful, and I have been able to figure it out:
As I am working in our office template, these settings over-ride the required floor plan cut plane. To get around this, you must right click the storey and select 'view settings'. In this box you can go to the Floor Plan Cut Plane Settings dialog box and insert your required value.
This will ensure the cut plane stays at the required value when switching between storeys.
Thanks,
Emily