[Yo-Yo]

The open fan has been tried before. It's main drawback is it is much noiser than a ducted fan. And if he plans to fly that thing in and out of Heathrow, noise is the number one problem.

That said, here is another Flight International article outlining the current research into unducted fans (UDFs.)

[Freeport]

Correct, but the arrangement shown, above & behind the fuselage, like other aircraft that make use of this arrangement, does reduce / eliminate the noise problem in the aircraft.

But I wouldn’t want to live on the runway approaches!