Hmm, well looks like I can answer my own question on this one - Intaserve seem to reg. the domain as soon as they process your payment.
Good questions. I'm not sure.
But I do know that Cheaper Domains automatically registers once payment is approved UNLESS something in the order gets flagged for manual review.
I'm not sure how many other registrars have completely automated systems.
I thought all registrars had to manually approve an application/registration as a rule
I thought all registrars had to manually approve an application/registration as a rule