So after a month of pop-ups from FireFox telling me how it's critically out of date, i decided to update from 61 to 62.02
The Inspect Element tool has now gone from 2 windows to 3 windows, OK for big screens although it was fine how it was! but when trying to inspect elements on small screens and check responsive elements it's awful.
Anyone know of a better plug-in for FireFox? or a way to turn the 3rd window off?