Hi Grant,
This module https://marketplace.mendix.com/link/component/117034 allows you to use an Exel template and populate the fields using the attributes of an entity. I think this will be useful.
If you need more flexibility, use: https://marketplace.mendix.com/link/component/116370.
Go Make It
I was able to sort this myself by creating a new hidden sheet in Excel to export my data to. The columns which need to be populated by my Case Information now just point to the Exported columns in the hidden sheet.
There was also an issue with my Join Types in the Export Worksheet hence why I wasn't able to see my data in the exported template. I have now resolved by changing the Associations within the Excel Export Worksheet settings to LEFT JOIN.