Needed help with data model and building matrix visual

In your case you need to get your permissions table transformed to include a row for each combination. In this case the key should be a combination of the Home branch and the Group, meaning that there will have to be two rows for the tariffs & rates permission. 

Once you have all different combinations of keys in the permissions table you can add a distinct version of that column as a seperate query, which you then use as a mapping table between the people and the permissionstable. 

Br,
J