...that prevented sensible error message being displayed if you try and signup a new member who has already completed the signup process

Similar fixes need to be handled in the susignup component

Allows staff to start sign up process for students who have paid but not yet signed up, including those who don't have their SU transaction ID.

Should coexist peacefully with existing signup system and the new SU signup component

Added initial version of SU API implementation for freshers fayre, still needs error checking adding, though now ready for testing, improvements welcome.