[eluser]warrennz[/eluser]
Thanks again Over Zealous
And quite right, I have a validation rule setup like that for it. I did have a really strange problem with it however. If I entered nothing into the confirm_username input field, once the form was posted, it would take on the value of my username field. Only after I added a 'required' rule to the confirm_username rule did it work as one might expect. Dunno if that's a bug, my code, or my browser being silly with cache/cookies/session or whatever but yea.
So not sure how I'm gonna get around that one in future