Okay,
I think I have found the simpler solution, as this issue was raised back in 2017:
But the answer is in the reply from Tut.
In order to complete Box 8 and 9 you create customised tax codes of, for example:
20% - Import
20% - Export
and make the reporting category 20% in order for it to get onto the VAT report.
But the VAT Calculation Worksheet needs to pick these up and add them into Boxes 8 and 9, so there is a little development work that is required here.
What do you think??