i think its in the app form or the guidance notes, that its only a valid application if payment is received.

they should send the acknowledge letter saying they received your application and payment or they received your application and there is a problem with the payment.

i think the payment side is done by someone else and not UKBA, probably why its done instantly

totally unfair if its UKBA fault or the banks fault if you had the money in your account, but what do you do with the people who didnt have the money in their account ?