I've got this code working for a custom registration http://pastebin.com/f22b62162 (the file is titled "RegistrationForm.php") and it is writing FirstName, Surname, Email and Password to the database.
Where would be the best (or easiest - just learning this stuff) place to make this added data write to the member field of the database...
extending the Member() class maybe? I can't find it in the CMS...
Cheers