Thanks Craig, but still not updating.
Data now persists bit there is another problem in that when the form is called, the email field is blank which will be a problem with large forms if I only want to change one field.
I may be asking too much of DA to have the fields populated with the original data AND persist if validation fails.
When I open the server validation behavior from the behaviors panel I have the choice to validate as an email address or unique value but not both as I could when building the registration form with the "create security pages" wizard