Wow! Thank you so much for providing me with detailed information 
Since my last post I decided to follow this tutorial Velo Tutorial: Creating a Custom Registration Form with Code | Help Center | Wix.com which has allowed me to enter all the information I require directly into the Wix Site Members List and will also allow me to easily approve them. I’ve also decided to include a password as I’m sure this may be something I require, in the future.
So, with that in mind and the fact I still need to ignore the Wix Login (as, by default, this would allow users to signup just with email and password by following the pre-determined link) do the steps you mentioned still apply?
I know I’m punching above my weight to try and get this sorted. I understand all the logic, I’m just struggling with how to achieve it!
Your time is very much appreciated!
Rachel