I have now figured out how to do this. Is it common knowledge? i couldn't find an instruction in the help menu.
What I do for a string ensemble (V1, V2 Viola, Cello) is to save the piece "save as" V1. This retains the original score but a new score V1 is made.
I then call this up and go into the "parts set up" and dellete the other instruments i dont require for V1 from the table. Repeat for V2 etc.