Failed online signup

[#1]

When I joined Plusnet I did it over the phone. If I had done it online I would know the answer to this.
At some point toward the end of an online signup you are clearly asked to supply credit card details as well as Direct Debit details. I don't know which of these comes first.
My question is, after entering the credit card details is that the end of the order, or do you need to do something more to complete it? For example if it precedes the d/d ones then you need to do that.
Or maybe there is just a screen saying "Payment authorised - Click Continue to place your order"?
Maybe there is a "Click continue to place the order" at the end of everything?
My reason for asking is this thinkbroadband thread.

[#2]

Card details come first, where payment is taken for first month, ( although you can choose to use direct debit details instead for the first month) ,  you then submit your dd details,  this then completes the order.
Kind regards
Mike

[#3]

Thanks Mike. That could explain what happened to the OP of the linked thread - if they didn't enter the D/D details.

[#4]

But what happens if you choose not to enter your direct debit details? Can you continue, and if you can what comes next? Is there a final "Submit order button" or similar somewhere, or does it just submit finally from the d/d screen. What if you don't - is there another way out that still submits the order?