Adding an extra step to the ProcessPayment in a new Payment plugin

Hi,

I am developing a SagePayDirect plugin to use the integrated version of SagePay rather than the offsite or Iframe version.
I have built the basic plugin and installed it...

I know need to add an extra step in the ProcessPayment method.

After I click "next" on the paymentinfo view I need to show an extra view for further bank validation before it goes to the confirm page.

How do I go about it?  Are there any further tutorials on adding payment plugins that would help?

Thanks,
Ben