Has anyone bought a spare battery from the likes of Handtec or shops like these who sell them for around £76
I think they are copies but are they as good?
I don't know these specifically, however IMHO tread very carefully, I inherited one (non DJI batter) with a second hand Phantom 3 - the DJIGO software rejects battery as non DJI & disables aircraft startup. This aside from capabilities / risk of 3rd party battery. In summary don't is my advice.