For those templates that just don't have one...
Some of the parallax templates have 'back to top' buttons, but, annoyingly, most of them don't.
So, one of our developers coded a button than can be pasted into your site - and a 'back to top' button will display on every page. Plus, it'll only display once the user scrolls down a little.
It's a small, but pretty, piece of code.