Thanks to Herve for his excellent guide on the E6440. Following it I was able to get a fully working (per guide) Sierra install on an old laptop my work was throwing out.
Thought I would type a quick note about a few things I encountered along the way to help out others incase they do the same install.
First, for some reason, the first USB port I tried to use for installation threw up errors and would not reach the installation screen, switching the USB ports I used fixed this for whatever reason!
Second, headphone port audio was initially hissy. In order to fix this, I had to install the codeccommander fix from this thread: Note that, for me at least, the EAPD fix from that thread was not necessary and actually caused a kernel panic on startup on my machine until it was removed.