I have the same issue as well, during the latest update it went from 56% to 5% In 5-10mins and now won’t charge above 50% guess I will be sending it in....
Well you shouldn’t fly in London full stop... the River Thames is a helicopter flight path, even if you are flying at 10m high the FAA still hold the right to give you a massive fine!
I think I see what your trying to do... if you still haven’t got it to work it probably means you will have to spend the $100 for the remote hdmi module from Dji...