This is a question for @clavaque
Are patches to s2member still being accepted?
I’ve made a small number of patches to implement a Custom Registration/Profile Field for the UK postcodes. It’s implemented in exactly the same as the US Zipcode, Canadian Zipcode and US/Canadian Zip codes in only three files.
/src/includes/classes/custom-reg-fields.inc.php
/src/includes/menu-pages/menu-pages-s.js
/src/includes/s2member.js