I believe that we are not required to use external link templates at all, Andy. But if one chooses to use them, one can place them wherever one likes in the relevant citation.
I generally don't use these templates myself, but if I did, I would place them at the end of the relevant citation. Many other WikiTreers choose to replace the regular link with the template or to place the templates at the beginning of a citation.
I recommend that you choose one style and stick with it on profiles you manage and on orphan profiles that you edit. For profiles managed by others, you should follow the style that the other managers have chosen.