You can export payrun data from the drop-down at the bottom-left of the payrun page.
There are two different formats available.
This gives you a CSV with similar rows and columns to what you see on screen
This gives you a CSV with potentially multiple lines per employee.
There is a line for each editable amount on the payslip (ie, not PAYE, NI, etc).
This format can be used to import payments to a payun.