To fix it:
Access "Settings", click on the Facebook icon, click on settings and select "auto play on wifi only".
Click on the small triangle at the top right of your Facebook page.
Scroll down to "Videos" - click on it and move the slider to "off".
Access your App Settings and do the same.
Press the left button (next to the home key on the phone), then press "Settings".
The auto play option will then appear where you can update it.