Ok understood, is there a trace/component I can break on the board to stop the charge reaching the battery terminals (now that I will have a dc supply in there instead of the battery) - Without losing the auto on/off function of the solar panel

I wouldn't bother about the solar panel trying to feed the battery terminals, it's not powerful enough to overcome the charger..

 

Does the light have a separate light sensor for turning the lights on in darkness? Some use the solar cell for that and therefore would not work if you disconnect it.

 

Does the light have a separate light sensor for turning the lights on in darkness? Some use the solar cell for that and therefore would not work if you disconnect it.

This one just uses the voltage from the solar cell to determine day v night. Ok ill leave it as.

Thanks again everyone for their help on this!