A programmers whose job is to make these kinds of reports will already have information about postcodes and so on, and take less time than you. Tableau is quick at doing simple things, but takes a lot of learning to do complex things. Often, you will have to resort to custom scripts, creating views, etc. Often, it just won't have the ability to do certain things.
Anyone with any experience in drag and drop applications will tell you that once things get complex, it ends up taking much more time using the simple drag and drop solution as you spend all of your time trying to get it to do something that is outside of a basic drag and drop model.