Hey Nicolas!
These are both fine options, and good to know for the future, however I think I may have explained myself poorly.
You are correct that the "Domestic machines" Menu is working as I want the rest of them to work, it is drawing them into categories based on the product "Category" field, where as the rest of the menus are only allowing them to be in One category, due to it organising them from the "Brand" field.
And as you can only have one it can only be in that one category in the menu, as you can see in the image above.
I'm just not sure why the categories in the "Domestic machines" menu are populated with the "categories" field from the products and the categories in the other sections are populated by The "Brand" field.
I assumed it would just be an option that I was missing somewhere.
A good way to explain the issue I guess is with an example.
In domestic machines I have the Pfaff Quilt Expression 720, and it is both the sewing machines and quilting machines category (As it is both of those)
However, In the Pfaff menu that would not be the case, as in the pfaff menu it only gathers the data from the brand field.
Which in this case is "Pfaff quilting Machines" and therefore only ends up in that one location, when it should show up in "Pfaff sewing machines" and "Pfaff Quilting Machines" at the same time.
Sorry for the confusion, It feels like I've typed category 1000 times.