It is possible. You need to assign the region relationship to the country that you will be used as filters first.
after that, you can use country as your filter.
Thanks for the reply. Although this works for England, those regions are also in the GB subset too.
The relationships are as follows:
Region Region 1 Region 2 Region 3 Wales Wales England & Wales Great Britain Scotland Scotland Scotland Great Britain Northern England England & Wales Great Britain Midlands England England & Wales Great Britain Eastern England England & Wales Great Britain South West England England & Wales Great Britain
There are essentially 4 levels within a hierarchy, but I want to create 1 filter that tackles all 4 levels. It will include all possibilities from 'Region' field + England, England & Wales & Great Britain.
Hope this clarifies further.