D8 Views aggregation and field formatters

I'm just wondering if, when using aggregation in a view, that formatters for the data type should be available? I have a custom field type that is stored as an integer and I've got the aggregation settings to SUM. But there are no formatters to select from ... only the standard thousands marker, prefix and suffix. Should my other formatters be available or is the custom field type missing a plugin for Views?