Re: It's time...
"The big difference there is that the helicopter will be flying at a safe altitude and following a logged flight plan and communicating with air traffic control":
On the assumption that this was Class G airspace, the Heli driver doesn't have to be "communicating with air traffic control".
And if his tail boom was able to strike a - "small" - tree and he was doing an instruction outside of the home ATZ, then he wasn't "flying at a safe altitude" nor was following a logged flight plan... unless you think radioning "Tower, we'll be over there somewhere" constiutes "a logged flight plan".
Under UK ANOs (which tend to mirror JAA rules), IF the drone pilot was under 400ft and outside an ATZ - as the heli being near "a small tree" would indicate, as there aren't many small trees inside airfields or hovering at 400 AGL - then the drone pilot was doing nothing wrong.