Hi Paul..
Password length is governed by "/etc/default/security" file.
Inside that file you will find:
MIN_PASSWORD_LENGTH
This parameter controls the minimum length of new passwords. It is not applicable to the root user on an untrusted system.
MIN_PASSWORD_LENGTH=N New passwords must contain at least N characters. For untrusted systems N can be any value from 6 to 8. For trusted systems N can be any value from 6 to 80.
Hope this helps..
Don't fix what ain't broke