Just in case anyone googles this in future.
My fix was to cycle down the power of EVERYTHING on the tv including the tv.
Pull out the HDMIs
Slowly cycle devices back up one by one and make sure SIMPLINK is enabled on the TV and quickstart + is disabled.
TV will recognise the device as KODI when you power it on and after a few seconds plug in the HDMI
LG TVs are a flakey nightmare essentially.